every

The every utility checks if all elements in an array pass the provided test function. It returns true only if the predicate returns truthy for every single element. It short-circuits and returns false as soon as a non-matching element is found.

Implementation

View Source Code

import { assert } from '../function/assert';
import { IS_ARRAY_ERROR_MSG, isArray } from '../typed/isArray';
import type { Predicate } from '../types';

/**
 * Checks if all elements in an array pass a predicate function.
 *
 * @example
 * ```ts
 * const arr = [1, 2, 3, 4, 5];
 * const isEven = (num) => num % 2 === 0;
 * every(arr, isEven); // false
 * ```
 *
 * @param array - The array to check.
 * @param predicate - The predicate function to test each element.
 *
 * @returns true if all elements pass the predicate test, else false.
 *
 * @throws {TypeError} If the first argument is not an array.
 */
export function every<T>(array: T[], predicate: Predicate<T>) {
  assert(isArray(array), IS_ARRAY_ERROR_MSG, { args: { array }, type: TypeError });

  for (let index = 0; index < array.length; index++) {
    if (!predicate(array[index], index, array)) {
      return false;
    }
  }

  return true;
}

every.fp = true;

Features

• Isomorphic: Works in both Browser and Node.js.
• Short-circuiting: Stops execution as soon as a failure is found for better performance.
• Type-safe: Properly typed predicate support.

API

function every<T>(array: T[], predicate: (item: T, index: number, array: T[]) => boolean): boolean;

Parameters

• array: The array to check.
• predicate: The function to test each element. It receives:
  • item: The current element.
  • index: The index of the current element.
  • array: The original array.

Returns

• true if the predicate returns truthy for every element; otherwise, false.

Examples

Basic Validation

import { every } from '@vielzeug/toolkit';

const numbers = [2, 4, 6, 8];

// Check if all numbers are even
const allEven = every(numbers, (x) => x % 2 === 0); // true

Checking Object Collections

import { every } from '@vielzeug/toolkit';

const tasks = [
  { id: 1, completed: true },
  { id: 2, completed: true },
  { id: 3, completed: false },
];

// Check if all tasks are finished
const allDone = every(tasks, (t) => t.completed); // false

Implementation Notes

• Throws TypeError if the first argument is not an array.
• Returns true for an empty array (vacuous truth).
• Does not modify the original array.

See Also

• some: Check if any element satisfies a condition.
• filter: Get all elements that satisfy a condition.
• find: Get the first element that satisfies a condition.