• Dart

final blank = s == null || s.trim() == '';

• Dart

bool blank = s?.trim()?.isEmpty ?? true;

• Ada

Blank := Index_Non_Blank (Str) = 0;

• C

bool blank = true;
for (const char *p = s; *p; p++) {
	if (!isspace(*p)) {
		blank = false;
		break;
	}
}

• Clojure

(blank? s)

• Cobol

IDENTIFICATION DIVISION.
PROGRAM-ID. blank string.
DATA DIVISION.
WORKING-STORAGE SECTION.
01 BOOLEAN-BLANK     PIC X.
   88 BLANK          VALUE "T".
   88 NOT-BLANK      VALUE "F".
PROCEDURE DIVISION.
    IF s > SPACES
       SET BLANK     TO TRUE
    ELSE
       SET NOT-BLANK TO TRUE
    END-IF 	 	
STOP RUN.

• C++

bool blank = false;
if (s.empty() || std::all_of(s.begin(), s.end(), [](char c){return std::isspace(c);})) {
      blank = true;
}

• C#

bool blank = string.IsNullOrWhiteSpace(s);

• C#

bool blank = string.IsNullOrWhiteSpace(s);

• D

bool blank = s.all!isSpace;

• Elixir

blank = s == nil || String.length(String.trim s) == 0

• Erlang

Blank = string:is_empty(string:trim(S)).

• Fortran

blank = s == ''

• Go

blank := strings.TrimSpace(s) == ""

• Haskell

b = null (dropWhile isSpace s)

• Haskell

blank :: Bool
blank = all isSpace s

• JS

const blank = s == null || s.trim() === ''

• Java

boolean blank = s==null || s.isBlank();

• Java

boolean blank = StringUtils.isBlank(s);

• Java

boolean blank = s==null || s.strip().isEmpty();

• Java

boolean blank = s == null || s.isBlank();

• Kotlin

val blank = s.isNullOrBlank()

• Lisp

(setf blank (not (find #\space s :test-not #'eql)))

• Lua

 blank = (s == nil or #string.gsub(s, "^%s*(.-)%s*$", "%1") == 0)

• Obj-C

BOOL blank=![s stringByTrimmingCharactersInSet:NSCharacterSet.whitespaceCharacterSet].length;

• PHP

$blank = !trim($s);

• PHP

$blank = (empty(trim($s));

• Pascal

blank := trim(s) = '';

• Perl

$blank = !$s || $s=~/^\s*$/;

• Python

blank = not s or s.isspace()

• Python

blank = not s or \
        not any(x not in ws for x in s)

• Python

blank = not s or \
        not sub(r'\s+', '', s)

• Ruby

blank = s.nil? or s.strip.empty?

• Rust

let blank = s.chars().all(|c| c.is_whitespace());

• Rust

let blank = s.trim().is_empty();

• Scala

val blank = Option(s).forall(_.trim.isEmpty)

• Scheme

(define (empty-string? s)
  (= (string-length s) 0))

(define blank (empty-string? (string-trim s)))

• Smalltalk

blank := s isAllSeparators.

• VB

Dim blank As Boolean = String.IsNullOrWhitespace(s)