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JavaScript - Array every() Method

In JavaScript, the Array.every() method is used to check all elements in an array satisfy a specified condition. This method takes a "callback function" as an argument, which iterates on every element in the array. It returns "true" if all the elements in the array passes the specified condition in the callback function; otherwise, it returns "false".

This method does not execute the function for empty array elements. In addition to that, this method does not modify the original array.

The every() method in an ECMAScript5 (ES5) feature and it is supported in all modern browsers such as Chrome, Edge, Firefox, Safari, and Opera.

Syntax

Following is the syntax of JavaScript Array.every() method −

every(callbackFn, thisArg)

Parameters

This method accepts two parameters. The same is described below −

  • callbackFn − A function to be executed for each element in the array. It takes three arguments −
    • element − The current element being processed in the array.
    • index (optional) − The index of the current element being processed in the array.
    • array (optional) − The array every() was called upon.
  • thisArg (optional) − A value to be passed to the function as its this value.

Return value

This method returns a Boolean value as a result.

Examples

Example 1

In the following example, we are checking if all elements in the array are even numbers using the the JavaScript Array.every() method −

<html>
<body>
   <script>
      const numbers = [2, 4, 6, 8, 10];
      const result = numbers.every(num => num % 2 === 0);
      document.write(result);
   </script>
</body>
</html>

Output

It returns "true" as result because all the elements in the array satisfies the condition of the callback function.

true

Example 2

In this example, we are checking if every string in the fruits array starts with the letter 'S' by using a callback function −

<html>
<body>
   <script>
      const fruits = ['Strawberry', 'Apple', 'Banana', 'Cherry'];
      const result = fruits.every(fruit => fruit[0] === 'S');
      document.write(result);
   </script>
</body>
</html>

Output

It returns "false" as a result because not all elements in the array are starting with letter 'S'.

false

Example 3

Here, we are verifying if all elements in the array are greater than 0 −

<html>
<body>
   <script>
      const numbers = [2, 4, 6, -8, 10];
      const result = numbers.every(num => num > 0);
      document.write(result);
   </script>
</body>
</html>

Output

Since not all elements are greater than 0, it returns 'false'.

false

Example 4

In this example, the every() method checks if every element in the array is of the type 'number' by using a callback function −

<html>
<body>
   <script>
      const array = [1, 'two', 3, 'four'];
      const result = array.every(item => typeof item === 'number');
      document.write(result);
   </script>
</body>
</html>

Output

Since not all elements are of the type 'number', it returns 'false'.

false
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