Science Knowings: JavaScript Course For Social Media

Array.every() Method

Introduction to Array.every()

Welcome to the Array.every() method! This method is used to check if every element in an array passes a given test.

What is Array.every()?

Array.every() takes a callback function as an argument and applies it to each element in the array. If the callback function returns true for every element, Array.every() returns true. Otherwise, it returns false.

Syntax

array.every(callbackFunction)

How Array.every() Works

Array.every() iterates over each element in the array and passes it to the callback function. The callback function should return a boolean value indicating whether the element passes the test.

Parameters

  • callbackFunction: The function to be called for each element in the array.

The callback function

The callback function takes three arguments:

  1. currentValue: The current element being processed.
  2. index: The index of the current element.
  3. array: The array being processed.

The index argument

The index argument represents the index of the current element being processed. It can be used to access the element's position within the array.

The array argument

The array argument represents the array being processed. It can be used to access other elements in the array.

Return Value

Array.every() returns a boolean value indicating whether every element in the array passed the test.

Callback Return Values

The callback function should return a boolean value. If the callback function returns true, it indicates that the element passed the test. Otherwise, it indicates that the element failed the test.

Short Circuit Evaluation

Array.every() uses short circuit evaluation. This means that if the callback function returns false for any element, Array.every() will immediately return false and stop iterating over the array.

When to Use Array.every()

Array.every() is useful for checking if all elements in an array meet a certain condition. For example, you can use Array.every() to check if all elements in an array are greater than a certain value.

Example Use Cases

Here are a few examples of how you can use Array.every():

  • Check if all elements in an array are greater than 10:
  • const numbers = [11, 12, 13, 14, 15];
    const allGreater = numbers.every((number) => number > 10);
    // Output: true
  • Check if all elements in an array are even:
  • const numbers = [2, 4, 6, 8, 10];
    const allEven = numbers.every((number) => number % 2 === 0);
    // Output: true
  • Check if all elements in an array are strings:
  • const strings = ['a', 'b', 'c', 'd', 'e'];
    const allStrings = strings.every((string) => typeof string === 'string');
    // Output: true

Polyfill

If you need to support older browsers that do not support Array.every(), you can use a polyfill. Here is a simple polyfill for Array.every():

if (!Array.prototype.every) {
  Array.prototype.every = function(callback) {
    for (let i = 0; i < this.length; i++) {
      if (!callback(this[i], i, this)) {
        return false;
      }
    }
    return true;
  };
}

Next Topic: Array.some() Method

In the next session, we'll explore another array method, Array.some(). This method is used to check if any element in an array passes a given test. Follow us to learn more!