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isLesserEqual()

isLesserEqual<T>(threshold): (value) => boolean

Creates a predicate function that determines if a value is less than or equal to a threshold.

Type Parameters​

T​

T extends string | number

The type of the values (number or string)

Parameters​

threshold​

T

The threshold value to compare against

Returns​

(value): boolean

Parameters​

value​

T

Returns​

boolean

Remarks​

  • Pure function with no side effects
  • Uses JavaScript's <= operator for comparison
  • Works with both numbers and strings (lexicographic comparison for strings)
  • Inclusive comparison (equal values return true)
  • Useful for array filtering and functional composition

Example​

const isAtMost100 = isLesserEqual(100);
isAtMost100(50);  // true
isAtMost100(100); // true (inclusive)
isAtMost100(150); // false

const isAtMostM = isLesserEqual('M');
isAtMostM('A'); // true
isAtMostM('M'); // true
isAtMostM('Z'); // false

// Useful with arrays
const ages = [16, 18, 21, 25, 30];
const underAge = ages.filter(isLesserEqual(20)); // [16, 18]