The snippets are under the CC-BY-SA license.

Creative Commons Attribution-ShareAlike 3.0

Logo

Programming-Idioms.org

  • The snippets are under the CC-BY-SA license.
  • Please consider keeping a bookmark
  • (instead of printing)
JS Go
1
Print a literal string on standard output
document.write("Hello World!");
Alternative implementation:
console.log('Hello World');
fmt.Println("Hello World")
Alternative implementation:
package main
func main(){print("Hello World")}
2
Loop to execute some code a constant number of times
for (let i = 0; i < 10; i++) {
  console.log("Hello");
}
Alternative implementation:
let count = 0;
while (count < 10) {
  count++; 
  console.log('Hello');
};
Alternative implementation:
[...Array(10)].forEach(() => console.log('Hello'))
Alternative implementation:
console.log( 'Hello\n'.repeat(10) )
for i := 0; i < 10; i++ {
	fmt.Println("Hello")
}
Alternative implementation:
fmt.Println(strings.Repeat("Hello\n", 10))
3
Like a function which doesn't return any value, thus has only side effects (e.g. Print to standard output)
var bli = function() { 
	console.log('Hello World!!!');
}
Alternative implementation:
function bli() { 
	console.log('Hello World!!!');
}
Alternative implementation:
let dog = 'Poodle';
const dogAlert = () => alert(dog);
func finish(name string) {
  fmt.Println("My job here is done. Good bye " + name)
}
Alternative implementation:
finish := func(name string) {
	fmt.Println("My job here is done. Good bye " + name)
}
4
Create a function which returns the square of an integer
function square(x) { 
	return x * x;
}
Alternative implementation:
const square = (x) => x * x;
Alternative implementation:
const square = n => n**2
Alternative implementation:
const square = (number) => Math.pow(number, 2);
func square(x int) int {
  return x*x
}
5
Declare a container type for two floating-point numbers x and y
var p = { x: 1.122, y: 7.45 };
Alternative implementation:
const point = { x: 1, y: 2 };
type Point struct {
    x, y float64
}
6
Do something with each item x of an array-like collection items, regardless indexes.
items.forEach((x) => {
    doSomething(x);
});
Alternative implementation:
for (x of items) {
	doSomething(x);
}
Alternative implementation:
items.forEach(doSomething)
Alternative implementation:
for (var i = 0; i<items.length; i++) {
  var x = items[i];
  doSomething(x);
}
Alternative implementation:
items.map(doSomething)
for _, x := range items {
    doSomething(x)
}
7
Print each index i with its value x from an array-like collection items
items.forEach((val, idx) => {
  console.log("index=" + idx + ", value=" + val);
});
Alternative implementation:
for (var i in items) {
   console.log("index=" + i + ", value=" + items[i]);
}
for i, x := range items {
    fmt.Printf("Item %d = %v \n", i, x)
}
8
Create a new map object x, and provide some (key, value) pairs as initial content.
const x = {one: 1, two:2}
Alternative implementation:
const x = new Map();
x.set("one", 1);
x.set("two", 2);
Alternative implementation:
const x = new Map([["one",1],["two",2]]);
x := map[string]int {"one": 1, "two": 2}
9
The structure must be recursive because left child and right child are binary trees too. A node has access to children nodes, but not to its parent.
class Node {
  constructor (data) {
    this.data = data
    this.left = null
    this.right = null
  }
}
type BinTree struct {
	Value valueType
	Left *BinTree
	Right *BinTree
}
10
Generate a random permutation of the elements of list x
for (var i = x.length - 1; i > 0; i--) {
    var j = Math.floor(Math.random() * (i + 1));
    var temp = x[j];
    x[j] = x[i];
    x[i] = temp;
}
for i := range x {
	j := rand.Intn(i + 1)
	x[i], x[j] = x[j], x[i]
}
Alternative implementation:
y := make([]T, len(x))
perm := rand.Perm(len(x))
for i, v := range perm {
	y[v] = x[i]
}
Alternative implementation:
rand.Shuffle(len(x), func(i, j int) {
	x[i], x[j] = x[j], x[i]
})
Alternative implementation:
for i := len(x) - 1; i > 0; i-- {
	j := rand.Intn(i + 1)
	x[i], x[j] = x[j], x[i]
}
11
The list x must be non-empty.
x[Math.floor(Math.random() * x.length)]
Alternative implementation:
x[~~(Math.random() * x.length)];
x[rand.Intn(len(x))]
Alternative implementation:
func pickT(x []T) T {
	return x[rand.Intn(len(x))]
}
12
Check if the list contains the value x.
list is an iterable finite container.
return list.indexOf(x) !== -1;
Alternative implementation:
return list.includes(x);
func Contains(list []T, x T) bool {
	for _, item := range list {
		if item == x {
			return true
		}
	}
	return false
}
13
Access each key k with its value x from an associative array mymap, and print them.
Object.entries(mymap).forEach(([key, value]) => {
	console.log('key:', key, 'value:', value);
});
Alternative implementation:
for (const key in mymap) {
    console.log('key:', key, 'value:', mymap[key]);
}
for k, x := range mymap {
  fmt.Println("Key =", k, ", Value =", x)
}
14
Pick a random number greater than or equals to a, strictly inferior to b. Precondition : a < b.
a + (b-a) * Math.random();
Alternative implementation:
a + Math.random() * (b - a)
func pick(a, b  float64)  float64 {
	return a + (rand.Float64() * (b-a))
}
15
Pick a random integer greater than or equals to a, inferior or equals to b. Precondition : a < b.
function pick(a, b) {
    return a + Math.floor(Math.random() * (b - a + 1));
}
func pick(a,b int) int {
	return a + rand.Intn(b-a+1)
}
16
Call a function f on every node of binary tree bt, in depth-first infix order
function dfs(bt) {
	if (bt === undefined) return;
	dfs(bt.left);
	f(bt);
	dfs(bt.right);
}
func (bt *BinTree) Dfs(f func(*BinTree)) {
	if bt == nil {
		return
	}
	bt.Left.Dfs(f)
	f(bt)
	bt.Right.Dfs(f)
}
17
The structure must be recursive. A node may have zero or more children. A node has access to its children nodes, but not to its parent.
class Node {
  constructor (value, children = []) {
    this.value = value
    this.children = children
  }
}
type Tree struct {
	Key keyType
	Deco valueType
	Children []*Tree
}
18
Call a function f on every node of a tree, in depth-first prefix order
function DFS(f, root) {
	f(root)
	if (root.children) {
		root.children.forEach(child => DFS(f, child))
	}
}
func (t *Tree) Dfs(f func(*Tree)) {
	if t == nil {
		return
	}
	f(t)
	for _, child := range t.Children {
		child.Dfs(f)
	}
}
19
Reverse the order of the elements of list x.
This may reverse "in-place" and destroy the original ordering.
x = x.reverse();
for i, j := 0, len(x)-1; i < j; i, j = i+1, j-1 {
	x[i], x[j] = x[j], x[i]
}
20
Implement a function search which looks for item x in a 2D matrix m.
Return indices i, j of the matching cell.
Think of the most idiomatic way in the language to return the two values at the same time.
function search(m, x) {
    for (var i = 0; i < m.length; i++) {
        for (var j = 0; j < m[i].length; j++) {
            if (m[i][j] == x) {
                return [i, j];
            }
        }
    }
    return false;
}
func search(m [][]int, x int) (bool, int, int) {
	for i := range m {
		for j, v := range m[i] {
			if v == x {
				return true, i, j
			}
		}
	}
	return false, 0, 0
}
21
Swap the values of the variables a and b
var tmp = a;
a = b;
b = tmp;
Alternative implementation:
[a, b] = [b, a];
a, b = b, a
22
Extract the integer value i from its string representation s (in radix 10)
let i = parseInt(s, 10)
Alternative implementation:
const i = Number(s);
Alternative implementation:
const i = +s
i, err  := strconv.Atoi(s) 
Alternative implementation:
i, err := strconv.ParseInt(s, 10, 0)
23
Given a real number x, create its string representation s with 2 decimal digits following the dot.
num.toFixed(2)
s := fmt.Sprintf("%.2f", x)
24
Declare a new string s and initialize it with the literal value "ネコ" (which means "cat" in japanese)
s = "ネコ";
s := "ネコ"
25
Share the string value "Alan" with an existing running process which will then display "Hello, Alan"
{
  // in file worker.js
  onmessage = ({data}) => {
    console.log (`Hello, ${data}`)
  }
}
{
  // in file main.js
  const worker = new Worker ('worker.js')
  worker.postMessage ('Alan')
}
Alternative implementation:
if (isMainThread) {
  const worker = new Worker(new URL(import.meta.url));
  worker.postMessage('Alan');
} else {
  parentPort.once('message', (message) => {
    console.log(`Hello, ${message}`);
  });
}
go func() {
	v := <-ch
	fmt.Printf("Hello, %v\n", v)
}()

ch <- "Alan"
26
Declare and initialize a matrix x having m rows and n columns, containing real numbers.
var x = [];
for (var i = 0; i < m; i++) {
  x[i] = [];
}
Alternative implementation:
const x = new Array(m).fill(new Array(n).fill(Math.random()));
const m, n = 3, 4
var x [m][n]float64
Alternative implementation:
func make2D(m, n int) [][]float64 {
	buf := make([]float64, m*n)

	x := make([][]float64, m)
	for i := range x {
		x[i] = buf[:n:n]
		buf = buf[n:]
	}
	return x
}
27
Declare and initialize a 3D array x, having dimensions boundaries m, n, p, and containing real numbers.
const x = new Array(m).fill(
  new Array(n).fill(
    new Array(p).fill(Math.random())
  )
)
const m, n, p = 2, 2, 3
var x [m][n][p]float64
Alternative implementation:
func make3D(m, n, p int) [][][]float64 {
	buf := make([]float64, m*n*p)

	x := make([][][]float64, m)
	for i := range x {
		x[i] = make([][]float64, n)
		for j := range x[i] {
			x[i][j] = buf[:p:p]
			buf = buf[p:]
		}
	}
	return x
}
28
Sort the elements of the list (or array-like collection) items in ascending order of x.p, where p is a field of the type Item of the objects in items.
items.sort(function(a,b) {
  return compareFieldP(a.p, b.p);
});
type ItemPSorter []Item
func (s ItemPSorter) Len() int{ return len(s) }
func (s ItemPSorter) Less(i,j int) bool{ return s[i].p<s[j].p }
func (s ItemPSorter) Swap(i,j int) { s[i],s[j] = s[j],s[i] }

func sortItems(items []Item){
	sorter := ItemPSorter(items)
	sort.Sort(sorter)
}
Alternative implementation:
less := func(i, j int) bool {
	return items[i].p < items[j].p
}
sort.Slice(items, less)
29
Remove i-th item from list items.
This will alter the original list or return a new list, depending on which is more idiomatic.
Note that in most languages, the smallest valid value for i is 0.
let new_list = items.filter(function(val,idx,ary) { return idx != i });
Alternative implementation:
items.splice(i,1);
items = append(items[:i], items[i+1:]...)
Alternative implementation:
copy(items[i:], items[i+1:])
items[len(items)-1] = nil
items = items[:len(items)-1]
30
Launch the concurrent execution of procedure f with parameter i from 1 to 1000.
Tasks are independent and f(i) doesn't return any value.
Tasks need not run all at the same time, so you may use a pool.
for (let i = 1; i <= 1000; i++) setTimeout(() => f(i), 0);
wg := sync.WaitGroup{}
wg.Add(1000)
for i := 1; i <= 1000; i++ {
	go func(j int) {
          f(j)
          wg.Done()
        }(i)
}
wg.Wait()
31
Create the recursive function f which returns the factorial of the non-negative integer i, calculated from f(i-1)
function f(i) {
   return i<2 ? 1 : i * f(i-1);
}
Alternative implementation:
const f = i => i === 0 ? 1 : i * f(i-1)
func f(i int) int {
  if i == 0 {
    return 1
  }
  return i * f(i-1)
}
32
Create function exp which calculates (fast) the value x power n.
x and n are non-negative integers.
function exp(x, n) {
   if (n===0) return 1;
   if (n===1) return x;
   return n%2 ? x * exp(x*x, (n-1)/2)
              : exp(x*x, n/2);
}
Alternative implementation:
const exp = Math.pow;
func exp(x, n int) int {
	switch {
	case n == 0:
		return 1
	case n == 1:
		return x
	case n%2 == 0:
		return exp(x*x, n/2)
	default:
		return x * exp(x*x, (n-1)/2)
	}
}
33
Assign to the variable x the new value f(x), making sure that no other thread may modify x between the read and the write.
let x = f(x)
var lock sync.RWMutex

lock.Lock()
x = f(x)
lock.Unlock()
34
Declare and initialize a set x containing unique objects of type T.
let x = new Set();
x := make(map[T]bool)
Alternative implementation:
x := make(map[T]struct{})
35
Implement a function compose (A -> C) with parameters f (A -> B) and g (B -> C), which returns composition function g ∘ f
function compose(f,g){
    return function(x){
        return g(f(x));
    };
}
func compose(f func(A) B, g func(B) C) func(A) C {
	return func(x A) C {
		return g(f(x))
	}
}
36
Implement a function compose which returns composition function g ∘ f for any functions f and g having exactly 1 parameter.
function compose(f,g){
    return function(x){
        return g(f(x));
    };
}
Alternative implementation:
const compose = f => g => x => g(f(x));
func composeIntFuncs(f func(int) int, g func(int) int) func(int) int {
	return func(x int) int {
		return g(f(x))
	}
}
37
Transform a function that takes multiple arguments into a function for which some of the arguments are preset.
function curry (fn, scope) {
   
    scope = scope || window;
    
    // omit curry function first arguments fn and scope
    var args = Array.prototype.slice.call(arguments, 2);
    
    return function() {
	var trueArgs = args.concat(Array.prototype.slice.call(arguments, 0));
        fn.apply(scope, trueArgs);
    };
}
Alternative implementation:
const curry = (fn, ...initialArgs) => (...args) => fn(...initialArgs, ...args);

const add = (a, b) => a + b;

const add5 = curry(add, 5);

const result = add5(1) // 6
type PayFactory func(Company, *Employee, *Employee) Payroll

type CustomPayFactory func(*Employee) Payroll

func CurryPayFactory(pf PayFactory,company Company, boss *Employee) CustomPayFactory {
	return func(e *Employee) Payroll {
		return pf(company, boss, e)
	}
}
38
Find substring t consisting in characters i (included) to j (excluded) of string s.
Character indices start at 0 unless specified otherwise.
Make sure that multibyte characters are properly handled.
let t = s.substring(i, j);
Alternative implementation:
let t = s.slice(i, j);
t := string([]rune(s)[i:j])
39
Set boolean ok to true if string word is contained in string s as a substring, or to false otherwise.
var ok = s.indexOf(word) !== -1;
Alternative implementation:
var ok = s.includes(word);
ok := strings.Contains(s, word)
40
Declare a Graph data structure in which each Vertex has a collection of its neighbouring vertices.
type Vertex struct{
	Id int
	Label string
	Neighbours map[*Vertex]bool
}

type Graph []*Vertex
41
Create string t containing the same characters as string s, in reverse order.
Original string s must remain unaltered. Each character must be handled correctly regardless its number of bytes in memory.
var t = s.split("").reverse().join("");
runes := []rune(s)
for i, j := 0, len(runes)-1; i < j; i, j = i+1, j-1 {
   runes[i], runes[j] = runes[j], runes[i]
}
t := string(runes)
42
Print each item v of list a which is not contained in list b.
For this, write an outer loop to iterate on a and an inner loop to iterate on b.
OUTER:
for (var i in a) {
   for (var j in b) {
      if (a[i] === b[j]) {
         continue OUTER;
      }
   }
   console.log(a[i] + " not in the list");
}
mainloop:
	for _, v := range a {
		for _, w := range b {
			if v == w {
				continue mainloop
			}
		}
		fmt.Println(v)
	}
43
Look for a negative value v in 2D integer matrix m. Print it and stop searching.
OUTER:
for (var i in m) {
   for (var j in m[i]) {
      if (m[i][j] < 0) {
         console.log("Negative value found: "+m[i][j]);
         break OUTER;
      }
   }
}
mainloop:
	for i, line := range m {
		for _, v := range line {
			if v < 0 {
				fmt.Println(v)
				break mainloop
			}
		}
	}
44
Insert element x at position i in list s. Further elements must be shifted to the right.
s.splice(i, 0, x);
s = append(s, 0)
copy(s[i+1:], s[i:])
s[i] = x
45
Sleep for 5 seconds in current thread, before proceeding with the next instructions.
setTimeout(function(){
	// Instructions after delay
},5000);
Alternative implementation:
const sleep = ms => new Promise(resolve => setTimeout(resolve, ms));

// use inside an async function
await sleep(5000);
time.Sleep(5 * time.Second)
46
Create string t consisting of the 5 first characters of string s.
Make sure that multibyte characters are properly handled.
let t = s.substring(0,5);
t := string([]rune(s)[:5])
47
Create string t consisting in the 5 last characters of string s.
Make sure that multibyte characters are properly handled.
var t = s.slice(-5);
t := string([]rune(s)[len([]rune(s))-5:])
48
Assign to variable s a string literal consisting in several lines of text, including newlines.
let s = "This is a very long string which needs \n" +
        "to wrap across multiple lines because \n" +
        "otherwise my code is unreadable.";
Alternative implementation:
let s = "This is a very long string which needs \
to wrap across multiple lines because \
otherwise my code is unreadable.";
Alternative implementation:
let s = `This is a very long string which needs 
to wrap across multiple lines because 
otherwise my code is unreadable.`;
s := `Huey
Dewey
Louie`
49
Build list chunks consisting in substrings of input string s, separated by one or more space characters.
let chunks = s.split(/ +/);
chunks := strings.Split(s, " ")
Alternative implementation:
chunks := strings.Fields(s)
50
Write a loop that has no end clause.
while (true) {
	// to infinity
}
Alternative implementation:
for(;;) {
	console.log('Oops')
}
for {
	// Do something
}
51
Determine whether the map m contains an entry for the key k
k in m
Alternative implementation:
m.hasOwnProperty(k)
Alternative implementation:
_m.has(_k)
_, ok := m[k]
52
Determine whether the map m contains an entry with the value v, for some key.
Object.values(m).includes(v)
Alternative implementation:
[...m.values()].includes(v)
func containsValue(m map[K]T, v T) bool {
	for _, x := range m {
		if x == v {
			return true
		}
	}
	return false
}
53
Concatenate elements of string list x joined by the separator ", " to create a single string y.
y = x.join(", ");
y := strings.Join(x, ", ")
54
Calculate the sum s of the integer list or array x.
var s = x.reduce((a, b) => a + b, 0);
Alternative implementation:
var s = x.reduce((a, b) => a + b)
s := 0
for _, v := range x {
	s += v
}
55
Create the string representation s (in radix 10) of the integer value i.
var s = i.toString();
Alternative implementation:
var s = i + "";
s := strconv.Itoa(i)
Alternative implementation:
s := strconv.FormatInt(i, 10)
Alternative implementation:
s := fmt.Sprintf("%d", i)
56
Fork-join : launch the concurrent execution of procedure f with parameter i from 1 to 1000.
Tasks are independent and f(i) doesn't return any value.
Tasks need not run all at the same time, so you may use a pool.
Wait for the completion of the 1000 tasks and then print "Finished".
{
  // in file worker.js
  onmessage = f
}
{
  // in file main.js
  for (let i = 0; i < 1000; i++) {
    new Worker ('worker.js')
      .postMessage (i)
  }
}
Alternative implementation:
const tasks = [];
for (let i = 0; i < 1000; i++) {
  tasks.push(f(i));
}

await Promise.all(tasks);
console.log("Finished");
var wg sync.WaitGroup
wg.Add(1000)
for i := 1; i <= 1000; i++ {
	go func(i int) {
		f(i)
		wg.Done()
	}(i)
}
wg.Wait()
fmt.Println("Finished")
57
Create the list y containing the items from the list x that satisfy the predicate p. Respect the original ordering. Don't modify x in-place.
y = x.filter(p);
y := make([]T, 0, len(x))
for _, v := range x{
	if p(v){
		y = append(y, v)
	}
}
Alternative implementation:
n := 0
for _, v := range x {
	if p(v) {
		n++
	}
}
y := make([]T, 0, n)
for _, v := range x {
	if p(v) {
		y = append(y, v)
	}
}
58
Create string lines from the content of the file with filename f.
fs.readFile(f, (err, lines) => {
    if (err) {
        // Handle error...
    }

    // Work with `lines` here.
}
b, err := ioutil.ReadFile(f)
if err != nil {
	// Handle error...
}
lines := string(b)
59
Print the message "x is negative" to standard error (stderr), with integer x value substitution (e.g. "-2 is negative").
console.error(util.format("%d is negative", x));
Alternative implementation:
console.error(x, "is negative");
Alternative implementation:
console.error(`${x} is negative`);
fmt.Fprintln(os.Stderr, x, "is negative")
60
Assign to x the string value of the first command line parameter, after the program name.
const x = process.argv[2]
x := os.Args[1]
61
Assign to the variable d the current date/time value, in the most standard type.
var d = Date.now();
Alternative implementation:
var d = new Date();
d := time.Now()
62
Set i to the first position of string y inside string x, if exists.

Specify if i should be regarded as a character index or as a byte index.

Explain the behavior when y is not contained in x.
let i = x.indexOf(y);
i := strings.Index(x, y)
63
Assign to x2 the value of string x with all occurrences of y replaced by z.
Assume occurrences of y are not overlapping.
var x2 = x.replace(new RegExp(y, 'g'), z);
Alternative implementation:
const x2 = x.replaceAll(y, z);
x2 := strings.Replace(x, y, z, -1)
64
Assign to x the value 3^247
let x = 3n ** 247n;
x := new(big.Int)
x.Exp(big.NewInt(3), big.NewInt(247), nil)
65
From the real value x in [0,1], create its percentage string representation s with one digit after decimal point. E.g. 0.15625 -> "15.6%"
const s = Math.round (x * 1000) / 10 + '%'
Alternative implementation:
const percentFormatter = new Intl.NumberFormat('en-US', {
  style: 'percent',
  maximumSignificantDigits: 3
});

const s = percentFormatter.format(x);
s := fmt.Sprintf("%.1f%%", 100.0*x)
66
Calculate the result z of x power n, where x is a big integer and n is a positive integer.
let z = x**n
nb := big.NewInt(int64(n))
var z big.Int
z.Exp(x, nb, nil)
67
Calculate binom(n, k) = n! / (k! * (n-k)!). Use an integer type able to handle huge numbers.
const fac = x => x ? x * fac (x - 1) : x + 1
const binom = (n, k) => fac (n) / fac (k) / fac (n - k >= 0 ? n - k : NaN)
z := new(big.Int)
z.Binomial(n, k)
68
Create an object x to store n bits (n being potentially large).
let x = new Buffer (Math.ceil (n / 8))
var x *big.Int = new(big.Int)
Alternative implementation:
x := make([]bool, n)
Alternative implementation:
x := make([]uint64, (n+63)/64)
69
Use seed s to initialize a random generator.

If s is constant, the generator output will be the same each time the program runs. If s is based on the current value of the system clock, the generator output will be different each time.
seed (s)
rand.Seed(s)
Alternative implementation:
r := rand.New(rand.NewSource(s))
70
Get the current datetime and provide it as a seed to a random generator. The generator sequence will be different at each run.
Math.random ()
rand.Seed(time.Now().UnixNano())
Alternative implementation:
r := rand.New(rand.NewSource(time.Now().UnixNano()))
71
Basic implementation of the Echo program: Print all arguments except the program name, separated by space, followed by newline.
The idiom demonstrates how to skip the first argument if necessary, concatenate arguments as strings, append newline and print it to stdout.
console.log(process.argv.slice(2).join(" "));
func main() {
    fmt.Println(strings.Join(os.Args[1:], " "))
}
73
Create a factory named fact for any sub class of Parent and taking exactly one string str as constructor parameter.
class Parent {
    constructor(str) {}
    fact(new_class, str) {
        if (new_class.prototype instanceof Parent) {
            return new new_class(str)
        }
    }
}

class Child extends Parent {}
type ParentFactory func(string) Parent

var fact ParentFactory = func(str string) Parent {
	return Parent{
		name: str,
	}
}
74
Compute the greatest common divisor x of big integers a and b. Use an integer type able to handle huge numbers.
const gcd = (a, b) => b === 0 ? a : gcd (b, a % b)
x.GCD(nil, nil, a, b)
75
Compute the least common multiple x of big integers a and b. Use an integer type able to handle huge numbers.
const gcd = (a, b) => b === 0 ? a : gcd (b, a % b)
let x = (a * b) / gcd(a, b)
gcd.GCD(nil, nil, a, b)
x.Div(a, gcd).Mul(x, b)
76
Create the string s of integer x written in base 2.

E.g. 13 -> "1101"
let s = x.toString(2);
s := strconv.FormatInt(x, 2)
Alternative implementation:
s := fmt.Sprintf("%b", x)
77
Declare a complex x and initialize it with value (3i - 2). Then multiply it by i.
var x = math.complex(-2, 3);
x = math.multiply(x, math.i);
x := 3i - 2
x *= 1i
78
Execute a block once, then execute it again as long as boolean condition c is true.
do {
   something();
} while (c);
for{
   someThing()
   someOtherThing()
   if !c {
     break
   }
}
Alternative implementation:
for done := false; !done; {
	someThing()
	someOtherThing()
	done = !c()
}
79
Declare the floating point number y and initialize it with the value of the integer x .
let y = x + .0
y := float64(x)
80
Declare integer y and initialize it with the value of floating point number x . Ignore non-integer digits of x .
Make sure to truncate towards zero: a negative x must yield the closest greater integer (not lesser).
let y = BigInt (x | 0)
y := int(x)
81
Declare integer y and initialize it with the rounded value of floating point number x .
Ties (when the fractional part of x is exactly .5) must be rounded up (to positive infinity).
var y = Math.round(x);
y := int(math.Floor(x + 0.5))
82
Find how many times string s contains substring t.
Specify if overlapping occurrences are counted.
let n = 0 // the number of occurences
let acc = s
let i
while ((i = acc.indexOf (t)) + 1) {
  n++
  acc = acc.slice (i + 1)
}
x := strings.Count(s, t)
83
Declare regular expression r matching strings "http", "htttp", "httttp", etc.
const r = /htt+p/
r := regexp.MustCompile("htt+p")
84
Count number c of 1s in the integer i in base 2.

E.g. i=6 → c=2
const c = i.toString(2).replace(/[^1]/g, '').length
func PopCountUInt64(i uint64) (c int) {
	i -= (i >> 1) & 0x5555555555555555
	i = (i>>2)&0x3333333333333333 + i&0x3333333333333333
	i += i >> 4
	i &= 0x0f0f0f0f0f0f0f0f
	i *= 0x0101010101010101
	return int(i >> 56)
}

func PopCountUInt32(i uint32) (n int) {
	i -= (i >> 1) & 0x55555555
	i = (i>>2)&0x33333333 + i&0x33333333
	i += i >> 4
	i &= 0x0f0f0f0f
	i *= 0x01010101
	return int(i >> 24)
}
Alternative implementation:
c := bits.OnesCount(i)
85
Write boolean function addingWillOverflow which takes two integers x, y and return true if (x+y) overflows.

An overflow may be above the max positive value, or below the min negative value.
function addingWillOverflow(x, y) {
  return x > 0 && y > 0 && x > Number.MAX_SAFE_INTEGER - y
}
func addingWillOverflow(x int, y int) bool {
	if x > 0 {
		return y > math.MaxInt-x
	}
	return y < math.MinInt-x
}
86
Write boolean function multiplyWillOverflow which takes two integers x, y and return true if (x*y) overflows.

An overflow may be above the max positive value, or below the min negative value.
func multiplyWillOverflow(x, y uint64) bool {
   if x <= 1 || y <= 1 {
     return false
   }
   d := x * y
   return d/y != x
}
87
Exit immediately.
If some extra cleanup work is executed by the program runtime (not by the OS itself), describe it.
process.exit()
os.Exit(0)
88
Create a new bytes buffer buf of size 1,000,000.
let buf = new Buffer (1e6)
buf := make([]byte, 1_000_000)
89
You've detected that the integer value of argument x passed to the current function is invalid. Write the idiomatic way to abort the function execution and signal the problem.
throw new Error ('x is invalid')
return nil, fmt.Errorf("invalid value for x: %v", x)
90
Expose a read-only integer x to the outside world while being writable inside a structure or a class Foo.
const Foo = function Counter () {
  let n = 0
  Object.defineProperty (this, 'value', {get: () => n++})
}
{
  const counter = new Foo ()
  counter.value // 0
  counter.value // 1
}
Alternative implementation:
class Foo {
  #x = 123;
  get x() {
    return this.#x;
  }
}
type Foo struct {
	x int
}

func (f *Foo) X() int {
	return f.x
}
91
Read from the file data.json and write its content into the object x.
Assume the JSON data is suitable for the type of x.
const x = JSON.parse(fs.readFileSync('./data.json'));
Alternative implementation:
const x = require('./data.json');
buffer, err := ioutil.ReadFile("data.json")
if err != nil {
	return err
}
err = json.Unmarshal(buffer, &x)
if err != nil {
	return err
}
Alternative implementation:
r, err := os.Open(filename)
if err != nil {
	return err
}
decoder := json.NewDecoder(r)
err = decoder.Decode(&x)
if err != nil {
	return err
}
92
Write the contents of the object x into the file data.json.
fs.writeFileSync('data.json', JSON.stringify(x));
buffer, err := json.MarshalIndent(x, "", "  ")
if err != nil {
	return err
}
err = ioutil.WriteFile("data.json", buffer, 0644)
93
Implement procedure control which receives one parameter f, and runs f.
function control(f){
	f();
}
func control(f func()) {
	f()
}
94
Print the name of the type of x. Explain if it is a static type or dynamic type.

This may not make sense in all languages.
console.log(typeof x);
Alternative implementation:
console.log (x == null ? x + '' : x.constructor.name);
fmt.Println(reflect.TypeOf(x))
Alternative implementation:
fmt.Printf("%T", x)
95
Assign to variable x the length (number of bytes) of the local file at path.
let x = read(path).length
info, err := os.Stat(path)
if err != nil {
	return err
}
x := info.Size()
96
Set boolean b to true if string s starts with prefix prefix, false otherwise.
var b = s.startsWith(prefix);
Alternative implementation:
var b = (s.lastIndexOf(prefix, 0) === 0);
b := strings.HasPrefix(s, prefix)
97
Set boolean b to true if string s ends with string suffix, false otherwise.
var b = s.endsWith(suffix);
b := strings.HasSuffix(s, suffix)
98
Convert a timestamp ts (number of seconds in epoch-time) to a date with time d. E.g. 0 -> 1970-01-01 00:00:00
new Date (ts * 1000)
d := time.Unix(ts, 0)
99
Assign to the string x the value of the fields (year, month, day) of the date d, in format YYYY-MM-DD.
let x = d.toISOString().slice(0, 10 /* 'yyyy-mm-dd'.length */)
Alternative implementation:
const today = new Date();
const isoDate = today.toISOString().slice(0, 10);
x := d.Format("2006-01-02")
100
Sort elements of array-like collection items, using a comparator c.
items.sort(c);
type ItemCSorter []Item
func (s ItemCSorter) Len() int           { return len(s) }
func (s ItemCSorter) Less(i, j int) bool { return c(s[i], s[j]) }
func (s ItemCSorter) Swap(i, j int)      { s[i], s[j] = s[j], s[i] }

func sortItems(items []Item) {
	sorter := ItemCSorter(items)
	sort.Sort(sorter)
}
Alternative implementation:
type ItemsSorter struct {
	items []Item
	c     func(x, y Item) bool
}

func (s ItemsSorter) Len() int           { return len(s.items) }
func (s ItemsSorter) Less(i, j int) bool { return s.c(s.items[i], s.items[j]) }
func (s ItemsSorter) Swap(i, j int)      { s.items[i], s.items[j] = s.items[j], s.items[i] }

func sortItems(items []Item, c func(x, y Item) bool) {
	sorter := ItemsSorter{
		items,
		c,
	}
	sort.Sort(sorter)
}
Alternative implementation:
sort.Slice(items, func(i, j int) bool {
	return c(items[i], items[j])
})
101
Make an HTTP request with method GET to the URL u, then store the body of the response in the string s.
$.get(u, function(data){
  s = data;
});
Alternative implementation:
var xmlHttp = new XMLHttpRequest();
xmlHttp.onreadystatechange = function() { 
	if (xmlHttp.readyState == 4 && xmlHttp.status == 200)
		s = xmlHttp.responseText;
}
xmlHttp.open("GET", u, true);
xmlHttp.send(null);
Alternative implementation:
fetch(u)
  .then(res => res.text())
  .then(text => s = text)
Alternative implementation:
const res = await fetch(u)
s = await res.text()
res, err := http.Get(u)
if err != nil {
	return err
}
buffer, err := ioutil.ReadAll(res.Body)
res.Body.Close()
if err != nil {
	return err
}
s := string(buffer)
102
Make an HTTP request with method GET to URL u, then store the body of the response in file result.txt. Try to save the data as it arrives if possible, without having all its content in memory at once.
resp, err := http.Get(u)
if err != nil {
	return err
}
defer resp.Body.Close()
if resp.StatusCode != 200 {
	return fmt.Errorf("Status: %v", resp.Status)
}
out, err := os.Create("result.txt")
if err != nil {
	return err
}
defer out.Close()
_, err = io.Copy(out, resp.Body)
if err != nil {
	return err
}
103
Read from the file data.xml and write its contents into the object x.
Assume the XML data is suitable for the type of x.
buffer, err := ioutil.ReadFile("data.xml")
if err != nil {
	return err
}
err = xml.Unmarshal(buffer, &x)
if err != nil {
	return err
}
104
Write the contents of the object x into the file data.xml.
buffer, err := xml.MarshalIndent(x, "", "  ")
if err != nil {
	return err
}
err = ioutil.WriteFile("data.xml", buffer, 0644)
105
Assign to the string s the name of the currently executing program (but not its full path).
var s = process.argv0;
path := os.Args[0]
s = filepath.Base(path)
Alternative implementation:
path, err := os.Executable()
if err != nil {
  panic(err)
}
s = filepath.Base(path)
106
Assign to string dir the path of the working directory.
(This is not necessarily the folder containing the executable itself)
let dir = process.cwd ()
dir, err := os.Getwd()
107
Assign to string dir the path of the folder containing the currently running executable.
(This is not necessarily the working directory, though.)
const dir = path.resolve();
Alternative implementation:
const dir = __dirname;
programPath := os.Args[0]
absolutePath, err := filepath.Abs(programPath)
if err != nil {
	return err
}
dir := filepath.Dir(absolutePath)
108
Print the value of variable x, but only if x has been declared in this program.
This makes sense in some languages, not all of them. (Null values are not the point, rather the very existence of the variable.)
if (typeof x !== 'undefined') {
    console.log(x);
}
Alternative implementation:
try {
	console.log(x);
} catch (e) {
	if (!e instanceof ReferenceError) {
		throw e;
	}
}
109
Set n to the number of bytes of a variable t (of type T).
var t T
tType := reflect.TypeOf(t)
n := tType.Size()
110
Set the boolean blank to true if the string s is empty, or null, or contains only whitespace ; false otherwise.
const blank = s == null || s.trim() === ''
blank := strings.TrimSpace(s) == ""
111
From current process, run program x with command-line parameters "a", "b".
exec(`${x} a b`);
err := exec.Command("x", "a", "b").Run()
112
Print each key k with its value x from an associative array mymap, in ascending order of k.
[...mymap.entries()].sort().map(([_, x]) => console.log(x))
keys := make([]string, 0, len(mymap))
for k := range mymap {
	keys = append(keys, k)
}
sort.Strings(keys)

for _, k := range keys {
	x := mymap[k]
	fmt.Println("Key =", k, ", Value =", x)
}
113
Print each key k with its value x from an associative array mymap, in ascending order of x.
Note that multiple entries may exist for the same value x.
Object.entries(mymap)
  .sort((a, b) => a[1] - b[1])
  .forEach(([key, value]) => {
    console.log('key:', key, 'value:', value);
  });
type entry struct {
	key   string
	value int
}

type entries []entry
func (list entries) Len() int { return len(list) }
func (list entries) Less(i, j int) bool { return list[i].value < list[j].value }
func (list entries) Swap(i, j int) { list[i], list[j] = list[j], list[i] }

entries := make(entries, 0, len(mymap))
for k, x := range mymap {
	entries = append(entries, entry{key: k, values: x})
}
sort.Sort(entries)

for _, e := range entries {
	fmt.Println("Key =", e.key, ", Value =", e.value)
}
Alternative implementation:
type entry struct {
	key   string
	value int
}

entries := make([]entry, 0, len(mymap))
for k, x := range mymap {
	entries = append(entries, entry{key: k, value: x})
}
sort.Slice(entries, func(i, j int) bool {
	return entries[i].value < entries[j].value
})

for _, e := range entries {
	fmt.Println("Key =", e.key, ", Value =", e.value)
}
114
Set boolean b to true if objects x and y contain the same values, recursively comparing all referenced elements in x and y.
Tell if the code correctly handles recursive types.
const b = JSON.stringify(x) === JSON.stringify(y);
Alternative implementation:
const arrayDeepEqual = (a, b) => a.length === b.length && a.every((x, i) => deepEqual(x, b[i]))

const deepEqual = (a, b) =>
  Array.isArray(a) && Array.isArray(b)
    ? arrayDeepEqual(a, b)
    : typeof a == 'object' && a && typeof b == 'object' && b
    ? arrayDeepEqual(Object.entries(a), Object.entries(b))
    : Number.isNaN(a) && Number.isNaN(b) || a === b

const b = deepEqual(x, y)
Alternative implementation:
const b = isDeepStrictEqual(x, y)
Alternative implementation:
const b = _.isEqual(x, y);
b := reflect.DeepEqual(x, y)
115
Set boolean b to true if date d1 is strictly before date d2 ; false otherwise.
let b = d1 < d2
b := d1.Before(d2)
116
Remove all occurrences of string w from string s1, and store the result in s2.
var regex = RegExp(w, 'g');
var s2 = s1.replace(regex, '');
Alternative implementation:
const s2 = s1.split(w).join('')
s2 := strings.Replace(s1, w, "", -1)
Alternative implementation:
s2 := strings.ReplaceAll(s1, w, "")
117
Set n to the number of elements of the list x.
var n = x.length;
n := len(x)
118
Create the set y from the list x.
x may contain duplicates. y is unordered and has no repeated values.
var y = new Set(x);
y := make(map[T]struct{}, len(x))
for _, v := range x {
	y[v] = struct{}{}
}
119
Remove duplicates from the list x.
Explain if the original order is preserved.
x = [...new Set(x)];
Alternative implementation:
x = Array.from(new Set(x));
Alternative implementation:
const seen = new Set();
x = x.filter( v => {
  if(seen.has(v))
    return false;
  seen.add(v);
  return true;
});
y := make(map[T]struct{}, len(x))
for _, v := range x {
	y[v] = struct{}{}
}
x2 := make([]T, 0, len(y))
for _, v := range x {
	if _, ok := y[v]; ok {
		x2 = append(x2, v)
		delete(y, v)
	}
}
x = x2
Alternative implementation:
seen := make(map[T]bool)
j := 0
for _, v := range x {
	if !seen[v] {
		x[j] = v
		j++
		seen[v] = true
	}
}
x = x[:j]
Alternative implementation:
seen := make(map[T]bool)
j := 0
for _, v := range x {
	if !seen[v] {
		x[j] = v
		j++
		seen[v] = true
	}
}
for i := j; i < len(x); i++ {
	x[i] = nil
}
x = x[:j]
120
Read an integer value from the standard input into the variable n
const {createInterface} = require('readline')

const rl = createInterface ({
  input: process.stdin,
  output: process.stdout
})

rl.question('Input an integer: ', response => {
  let n = parseInt (response)
  // stuff to be done with n goes here

  rl.close()
})
_, err := fmt.Scan(&n)
Alternative implementation:
_, err := fmt.Scanf("%d", &n)
121
Listen UDP traffic on port p and read 1024 bytes into buffer b.
ServerAddr,err := net.ResolveUDPAddr("udp",p)
if err != nil {
	return err
}
ServerConn, err := net.ListenUDP("udp", ServerAddr)
if err != nil {
	return err
}
defer ServerConn.Close()
n,addr,err := ServerConn.ReadFromUDP(b[:1024])
if err != nil {
	return err
}
if n<1024 {
	return fmt.Errorf("Only %d bytes could be read.", n)
}
122
Create an enumerated type Suit with 4 possible values SPADES, HEARTS, DIAMONDS, CLUBS.
const spades = 0
const hearts = 1
const diamonds = 2
const clubs = 3
type Suit int

const (
  Spades Suit = iota
  Hearts
  Diamonds
  Clubs
)
123
Verify that predicate isConsistent returns true, otherwise report assertion violation.
Explain if the assertion is executed even in production environment or not.
console.assert(_isConsistent);
if !isConsistent() {
	panic("State consistency violated")
}
124
Write the function binarySearch which returns the index of an element having the value x in the sorted array a, or -1 if no such element exists.
function binarySearch(a, x, i = 0) {
  if (a.length === 0) return -1
  const half = (a.length / 2) | 0
  return (a[half] === x) ?
    i + half :
    (a[half] > x) ?
    binarySearch(a.slice(0, half), x, i) :
    binarySearch(a.slice(half + 1), x, half + i + 1)
}
func binarySearch(a []T, x T) int {
	imin, imax := 0, len(a)-1
	for imin <= imax {
		imid := imin + (imax-imin) / 2
		switch {
		case a[imid] == x:
			return imid
		case a[imid] < x:
			imin = imid + 1
		default:
			imax = imid - 1
		}
	}
	return -1
}
Alternative implementation:
func binarySearch(a []int, x int) int {
	i := sort.SearchInts(a, x)
	if i < len(a) && a[i] == x {
		return i
	}
	return -1
}
Alternative implementation:
func binarySearch(a []T, x T) int {
	f := func(i int) bool { return a[i] >= x }
	i := sort.Search(len(a), f)
	if i < len(a) && a[i] == x {
		return i
	}
	return -1
}
125
measure the duration t, in nanoseconds, of a call to the function foo. Print this duration.
console.time('foo');
foo();
console.timeEnd('foo');
t1 := time.Now()
foo()
t := time.Since(t1)
ns := int64(t / time.Nanosecond)
fmt.Printf("%dns\n", ns)
Alternative implementation:
t1 := time.Now()
foo()
t := time.Since(t1)
ns := t.Nanoseconds()
fmt.Printf("%dns\n", ns)
126
Write a function foo that returns a string and a boolean value.
const foo = () => ({string: 'string', bool: true})
Alternative implementation:
const foo = () => ['string', true];
func foo() (string, bool) {
	return "Too good to be", true
}
127
Import the source code for the function foo body from a file "foobody.txt".
const foo = new Function(await readFile('foobody.txt'));
128
Call a function f on every node of a tree, in breadth-first prefix order
func (root *Tree) Bfs(f func(*Tree)) {
	if root == nil {
		return
	}
	queue := []*Tree{root}
	for len(queue) > 0 {
		t := queue[0]
		queue = queue[1:]
		f(t)
		queue = append(queue, t.Children...)
	}
}
129
Call the function f on every vertex accessible from the vertex start, in breadth-first prefix order
func (start *Vertex) Bfs(f func(*Vertex)) {
	queue := []*Vertex{start}
	seen := map[*Vertex]bool{start: true}
	for len(queue) > 0 {
		v := queue[0]
		queue = queue[1:]
		f(v)
		for next, isEdge := range v.Neighbours {
			if isEdge && !seen[next] {
				queue = append(queue, next)
				seen[next] = true
			}
		}
	}
}
130
Call th function f on every vertex accessible from the vertex v, in depth-first prefix order
func (v *Vertex) Dfs(f func(*Vertex), seen map[*Vertex]bool) {
	seen[v] = true
	f(v)
	for next, isEdge := range v.Neighbours {
		if isEdge && !seen[next] {
			next.Dfs(f, seen)
		}
	}
}
131
Execute f1 if condition c1 is true, or else f2 if condition c2 is true, or else f3 if condition c3 is true.
Don't evaluate a condition when a previous condition was true.
c1 ? f1 : c2 ? f2 : f3
Alternative implementation:
switch (true) {
  case c1:
    f1();
    break;
  case c2:
    f2();
    break;
  case c3:
    f3();
    break;
}
Alternative implementation:
if (c1) {
  f1();
} else if (c2) {
  f2();
} else if (c3) {
  f3();
}
switch {
case c1:
	f1()
case c2:
	f2()
case c3:
	f3()
}
132
Run procedure f, and return the duration of the execution of f.
function clock(f) {
  var start = new Date().getTime();
  f();
  var end = new Date().getTime();
  return end - start;
}
func clock(f func()) time.Duration {
	t := time.Now()
	f()
	return time.Since(t)
}
133
Set boolean ok to true if string word is contained in string s as a substring, even if the case doesn't match, or to false otherwise.
var lowerS = s.toLowerCase();
var lowerWord = word.toLowerCase();
var ok = lowerS.indexOf(lowerWord) !== -1;
lowerS, lowerWord := strings.ToLower(s), strings.ToLower(word)
ok := strings.Contains(lowerS, lowerWord)
134
Declare and initialize a new list items, containing 3 elements a, b, c.
const items = [a, b, c];
Alternative implementation:
const items = new Array(a, b, c);
items := []T{a, b, c}
135
Remove at most 1 item from list items, having value x.
This will alter the original list or return a new list, depending on which is more idiomatic.
If there are several occurrences of x in items, remove only one of them. If x is absent, keep items unchanged.
const idx = items.indexOf(x)
if (idx !== -1) items.splice(idx, 1)
for i, y := range items {
	if y == x {
		items = append(items[:i], items[i+1:]...)
		break
	}
}
Alternative implementation:
for i, y := range items {
	if y == x {
		copy(items[i:], items[i+1:])
		items[len(items)-1] = nil
		items = items[:len(items)-1]
		break
	}
}
136
Remove all occurrences of value x from list items.
This will alter the original list or return a new list, depending on which is more idiomatic.
const newlist = items.filter(y => x !== y)
items2 := make([]T, 0, len(items))
for _, v := range items {
	if v != x {
		items2 = append(items2, v)
	}
}
Alternative implementation:
j := 0
for i, v := range items {
	if v != x {
		items[j] = items[i]
		j++
	}
}
items = items[:j]
Alternative implementation:
j := 0
for i, v := range items {
	if v != x {
		items[j] = items[i]
		j++
	}
}
for k := j; k < len(items); k++ {
	items[k] = nil
}
items = items[:j]
137
Set the boolean b to true if the string s contains only characters in the range '0'..'9', false otherwise.
var b = /^[0-9]+$/.test(s);
b := true
for _, c := range s {
	if c < '0' || c > '9' {
		b = false
		break
	}
}
Alternative implementation:
isNotDigit := func(c rune) bool { return c < '0' || c > '9' }
b := strings.IndexFunc(s, isNotDigit) == -1
138
Create a new temporary file on the filesystem.
const tempFile = tempy.file()
Alternative implementation:
const resultOfCallback = tempy.file.task(tempFile => {
 // do something with tempFile
})
tmpfile, err := ioutil.TempFile("", "")
139
Create a new temporary folder on filesystem, for writing.
const tempDir = await Deno.makeTempDir();
dir, err := ioutil.TempDir("", "")
140
Delete from map m the entry having key k.

Explain what happens if k is not an existing key in m.
m.delete(k)
delete(m, k)
141
Iterate in sequence over the elements of the list items1 then items2. For each iteration print the element.
for (let item of items1) console.log(item)
for (let item of items2) console.log(item)
Alternative implementation:
items1.concat(items2).forEach(console.log)
for _, v := range items1 {
	fmt.Println(v)
}
for _, v := range items2 {
	fmt.Println(v)
}
142
Assign to string s the hexadecimal representation (base 16) of integer x.

E.g. 999 -> "3e7"
const s = x.toString(16)
s := strconv.FormatInt(x, 16)
Alternative implementation:
s := fmt.Sprintf("%x", x)
143
Iterate alternatively over the elements of the list items1 and items2. For each iteration, print the element.

Explain what happens if items1 and items2 have different size.
const shorter = _items1.length > _items2.length ? _items2 : _items1;
const longer = _items1.length <= _items2.length ? _items2 : _items1;
shorter.map((m, i) => {
  console.log(m);
  console.log(longer[i]);
});
Alternative implementation:
const iterator1 = items1[Symbol.iterator]()
const iterator2 = items2[Symbol.iterator]()

let result1 = iterator1.next()
let result2 = iterator2.next()

while(!(result1.done && result2.done)) {
  if (!result1.done) {
    console.log(result1.value)
    result1 = iterator1.next()
  }
  if (!result2.done) {
    console.log(result2.value)
    result2 = iterator2.next()
  }
}
for i := 0; i < len(items1) || i < len(items2); i++ {
	if i < len(items1) {
		fmt.Println(items1[i])
	}
	if i < len(items2) {
		fmt.Println(items2[i])
	}
}
144
Set boolean b to true if file at path fp exists on filesystem; false otherwise.

Beware that you should never do this and then in the next instruction assume the result is still valid, this is a race condition on any multitasking OS.
const b = fs.existsSync(fp);
Alternative implementation:
let b = true;
try {
	await access(fp);
} catch {
	b = false;
}
_, err := os.Stat(fp)
b := !os.IsNotExist(err)
145
Print message msg, prepended by current date and time.

Explain what behavior is idiomatic: to stdout or stderr, and what the date format is.
console.log(Date(), msg);
Alternative implementation:
console.error(Date(), msg);
log.Println(msg)
146
Extract floating point value f from its string representation s
let f = +s
f, err := strconv.ParseFloat(s, 64)
147
Create string t from string s, keeping only ASCII characters
const t = [...s].filter(c => c.charCodeAt(0) <= 0x7f).join('')
Alternative implementation:
const t = s.replace(/[^\x00-\x7f]/gu, '')
re := regexp.MustCompile("[[:^ascii:]]")
t := re.ReplaceAllLiteralString(s, "")
Alternative implementation:
t := strings.Map(func(r rune) rune {
	if r > unicode.MaxASCII {
		return -1
	}
	return r
}, s)
148
Read a list of integer numbers from the standard input, until EOF.
process.stdin.on('data', processLine)

function processLine (line) {
  const string = line + ''
  console.log(string)
}
Alternative implementation:
const ints = await new Promise(resolve => {
  let string = ''
  process.stdin
    .on('data', data => string += data.toString())
    .on('close', () => resolve(string.split('\n').map(line => Number.parseInt(line))))
})
var ints []int
s := bufio.NewScanner(os.Stdin)
s.Split(bufio.ScanWords)
for s.Scan() {
	i, err := strconv.Atoi(s.Text())
	if err == nil {
		ints = append(ints, i)
	}
}
if err := s.Err(); err != nil {
	return err
}
149
As an exception, this content is not under license CC BY-SA 3.0 like the rest of this website.
 
 
150
Remove last character from string p, if this character is a slash /.
const slashscrape = p => (
  p.slice (-1) === '/' ?
    p.slice (0, -1) :
    p
)
p = strings.TrimSuffix(p, "/")
151
Remove last character from string p, if this character is the file path separator of current platform.

Note that this also transforms unix root path "/" into the empty string!
p = p.endsWith(path.sep) ? p.slice(0, -path.sep.length) : p
sep := fmt.Sprintf("%c", os.PathSeparator)
p = strings.TrimSuffix(p, sep)
Alternative implementation:
sep := fmt.Sprintf("%c", filepath.Separator)
p = strings.TrimSuffix(p, sep)
152
Create string s containing only the character c.
let s = c
s := fmt.Sprintf("%c", c)
153
Create the string t as the concatenation of the string s and the integer i.
let t = s + i;
Alternative implementation:
let t = `${s}${i}`
t := fmt.Sprintf("%s%d", s, i)
Alternative implementation:
t := s + strconv.Itoa(i)
154
Find color c, the average between colors c1, c2.

c, c1, c2 are strings of hex color codes: 7 chars, beginning with a number sign # .
Assume linear computations, ignore gamma corrections.
var c = "#";
for(var i = 0; i<3; i++) {
  var sub1 = c1.substring(1+2*i, 3+2*i);
  var sub2 = c2.substring(1+2*i, 3+2*i);
  var v1 = parseInt(sub1, 16);
  var v2 = parseInt(sub2, 16);
  var v = Math.floor((v1 + v2) / 2);
  var sub = v.toString(16).toUpperCase();
  var padsub = ('0'+sub).slice(-2);
  c += padsub;
}
r1, _ := strconv.ParseInt(c1[1:3], 16, 0)
r2, _ := strconv.ParseInt(c2[1:3], 16, 0)
r := (r1 + r2) / 2

g1, _ := strconv.ParseInt(c1[3:5], 16, 0)
g2, _ := strconv.ParseInt(c2[3:5], 16, 0)
g := (g1 + g2) / 2

b1, _ := strconv.ParseInt(c1[5:7], 16, 0)
b2, _ := strconv.ParseInt(c2[5:7], 16, 0)
b := (b1 + b2) / 2

c := fmt.Sprintf("#%02X%02X%02X", r, g, b)
Alternative implementation:
var buf [7]byte
buf[0] = '#'
for i := 0; i < 3; i++ {
	sub1 := c1[1+2*i : 3+2*i]
	sub2 := c2[1+2*i : 3+2*i]
	v1, _ := strconv.ParseInt(sub1, 16, 0)
	v2, _ := strconv.ParseInt(sub2, 16, 0)
	v := (v1 + v2) / 2
	sub := fmt.Sprintf("%02X", v)
	copy(buf[1+2*i:3+2*i], sub)
}
c := string(buf[:])
155
Delete from filesystem the file having path filepath.
try {
  fs.unlinkSync(filepath);
} catch (err) {
  console.error(err);
}
Alternative implementation:
await unlink(filepath)
err := os.Remove(filepath)
156
Assign to the string s the value of the integer i in 3 decimal digits. Pad with zeros if i < 100. Keep all digits if i1000.
let s = i.toString();
if(i<100)
  s = ('00'+i).slice(-3);
s := fmt.Sprintf("%03d", i)
157
Initialize a constant planet with string value "Earth".
const planet = 'Earth'
const planet = "Earth"
158
Create a new list y from randomly picking exactly k elements from list x.

It is assumed that x has at least k elements.
Each element must have same probability to be picked.
Each element from x must be picked at most once.
Explain if the original ordering is preserved or not.
const idx = x.map((item, i) => i);
while (y.length < k) {
  const i = parseInt(Math.random() * idx.length, 10);
  y.push(x[[idx[i]]]);
  idx.splice(i, 1);
}
y := make([]T, k)
perm := rand.Perm(len(x))
for i, v := range perm[:k] {
	y[i] = x[v]
}
159
Define a Trie data structure, where entries have an associated value.
(Not all nodes are entries)
type Trie struct {
	c        rune
	children map[rune]*Trie
	isEntry  bool
	value    V
}
160
Execute f32() if platform is 32-bit, or f64() if platform is 64-bit.
This can be either a compile-time condition (depending on target) or a runtime detection.
const is64Bit = os.arch() === 'x64' || process.env.hasOwnProperty('PROCESSOR_ARCHITEW6432');
is64Bit ? _f64() : _f32();
if strconv.IntSize==32 {
	f32()
}
if strconv.IntSize==64 {
	f64()
}
161
Multiply all the elements of the list elements by a constant c
elements = elements.map(x => x * c)
for i := range elements {
	elements[i] *= c
}
162
execute bat if b is a program option and fox if f is a program option.
const args = process.argv.slice(2)
if (args.includes('b')) bat()
else if (args.includes('f')) fox()
var b = flag.Bool("b", false, "Do bat")
var f = flag.Bool("f", false, "Do fox")

func main() {
	flag.Parse()
	if *b {
		bar()
	}
	if *f {
		fox()
	}
}
163
Print all the list elements, two by two, assuming list length is even.
for (let index = 0; index < list.length; index = index + 2) {
  console.log(list[index], list[index + 1])
}
for i := 0; i+1 < len(list); i += 2 {
	fmt.Println(list[i], list[i+1])
}
164
Open the URL s in the default browser.
Set boolean b to indicate whether the operation was successful.
b := open.Start(s) == nil
Alternative implementation:
func openbrowser(url string) {
	var err error

	switch runtime.GOOS {
	case "linux":
		err = exec.Command("xdg-open", url).Start()
	case "windows":
		err = exec.Command("rundll32", "url.dll,FileProtocolHandler", url).Start()
	case "darwin":
		err = exec.Command("open", url).Start()
	default:
		err = fmt.Errorf("unsupported platform")
	}
	if err != nil {
		log.Fatal(err)
	}

}
165
Assign to variable x the last element of list items.
const x = items[items.length - 1];
Alternative implementation:
const x = items.at(-1);
x := items[len(items)-1]
166
Create the list ab containing all the elements of the list a, followed by all the elements of the list b.
var ab = a.concat(b);
ab := append(a, b...)
Alternative implementation:
var ab []T
ab = append(append(ab, a...), b...)
Alternative implementation:
ab := make([]T, len(a)+len(b))
copy(ab, a)
copy(ab[len(a):], b)
167
Create string t consisting of string s with its prefix p removed (if s starts with p).
if (s.indexOf(p) === 0) {
    t = s.substring(p.length);
}
t := strings.TrimPrefix(s, p)
168
Create string t consisting of string s with its suffix w removed (if s ends with w).
const t = s.endsWith(w) ? s.slice(0, -w.length) : s