TypeScript Array every() Method

The Array.every() method is an inbuilt TypeScript function that checks if all elements in an array pass the test implemented by the provided function. It returns true if every element satisfies the test; otherwise, it returns false.

Syntax

array.every(callback[, thisObject])

Parameter: This method accepts two parameters as mentioned above and described below:

• callback: The function to test for each element. It takes three arguments:
• thisObject: This parameter is the Object to use as this when executing callback.

Return Value: This method returns true if every element in this array satisfies the provided testing function. 

The below examples illustrate Array every() method in TypeScript

Example 1: Checking if All Elements are Positive

In this example The every() method checks if all elements in numbers are greater than 0, returning true because all numbers in the array [1, 2, 3, 4, 5] meet the condition.

let numbers: number[] = [1, 2, 3, 4, 5];
let allPositive: boolean = numbers.every(num => num > 0);

console.log(allPositive);  // Output: true

Output: 

true

Example 2: Checking if All Elements are Even

In this example the every() method checks if all elements in numbers are even, returning false because not all numbers in the array [1, 2, 3, 4, 5] are even.

let numbers: number[] = [1, 2, 3, 4, 5];
let allEven: boolean = numbers.every(num => num % 2 === 0);

console.log(allEven);  // Output: false

Output: 

false