JavaScript Glossary: Array .every() Method

Celý článek

Basics

The every method checks that each element in an array passes a set test. This method will return true if all the elements pass the set. Once an element that fails the test is found, the method returns false.

let result = [10, 5, 20, 100].every(function(number){
    return number < 150
})
console.log(result) // true

https://scotch.io/embed/gist/f792890d0a8ec4f3340d0e7dd27c6aa0

The every method:

• Takes a callback function that implements a test
• Checks if all the elements pass the test
• Returns true if every element passes the test.
• Returns false an element fails test

Syntax

const isCorrect = array.every(callback[,thisArg])

2 Parameters

callbackFunction(function) The function that tests each of the elements of the array. The callback function is required and can take three parameters:

• element: This is the element currently being executed - required.
• index: The index of the current item - optional.
• array: The array that is currently being processed - optional.

thisArg (this) (optional) An argument passed to be used as the this value in the callback - optional

Returns a single boolean value

This method will return true of every element in the array passes the test and if the array is empty. It returns false if an element within the array fails the test.

Common Uses and Snippets

Test an array for a matching threshold

When expecting a boolean return value after testing all the elements within an array.

https://scotch.io/embed/gist/8152e3ad8f6f952b14caad1e931b167f

Testing an array of Objects

.every() method can be used to test all items in an array of objects using either the object keys.

https://scotch.io/embed/gist/e53b9e8963170a4212278361adbec150