• Go

const alphanum = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"

func randomString(n int, rng *rand.Rand) string {
	a := make([]byte, n)
	for i := range a {
		a[i] = alphanum[rng.Intn(len(alphanum))]
	}
	return string(a)
}

• Go

const alphanum = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"

func randomString(n int) string {
	a := make([]byte, n)
	for i := range a {
		a[i] = alphanum[rand.Intn(len(alphanum))]
	}
	return string(a)
}

• Go

var alphanum = []rune("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789")

func randomString(n int, rng *rand.Rand) string {
	a := make([]rune, n)
	for i := range a {
		a[i] = alphanum[rng.Intn(len(alphanum))]
	}
	return string(a)
}

• JS

const s = ((n) => {
    const alphanum = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
    let s = "";
    for (let i = 0; i < n; i += 1) {
        s += alphanum[~~(Math.random() * alphanum.length)];
    }
    return s;
})(n);

• Java

public static String generateValues(int n)
{
	String alphabet1 = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
	String alphabet2 = "abcdefghijklmnopqrstuvwxyz";
	String digits = "0123456789";
	String values = alphabet1 + alphabet2 + digits;
		
	Random random = new Random(1);
	String s = "";
	for(int count = 0; count < n; count++) {
		s += String.valueOf(values.charAt(random.nextInt(values.length())));
	}
	
	return s;
}

• Pascal

function RandomString(Size: Integer): String;
const
  Chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
  Len = Length(Chars);
var
  i: Integer;
begin
  Result := '';
  SetLength(Result, Size);
  for i := 1 to Size do
  begin
    Result[i] := Chars[Random(Len)+1];
  end;
end; 

• Perl

my @chars = ('A'..'Z', 'a'..'z', '0'..'9'); 
my $s=''; 
$s .= $chars[int rand @chars] for 1..$n;

• Python

alphanum = string.ascii_letters + string.digits
s = ''.join(random.choices(alphanum, k=n))

• Ruby

s = SecureRandom.alphanumeric(n)

• Rust

fn random_string(n: usize) -> String {
    rand::thread_rng()
        .sample_iter(Alphanumeric)
        .take(n)
        .map(char::from)
        .collect()
}

• Rust

fn random_string(n: usize) -> String {
    Alphanumeric.sample_string(&mut rand::thread_rng(), n)
}