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The every() Array Methods in JavaScript and how to use it .

By Gopal Baskota
Published in JavaScript
January 03, 2021
1 min read

The every method checks that each element in an array passes a given condition. This method will return true if all the elements pass the condition. if an element fails that condition , the method returns false.

  • Iterates through an array
  • Runs a callback on each value in the array
  • If the callback returns false for any single value, return false
  • Otherwise, return true
  • the result of the callback will always be a boolean

An Example

let numbers = [1,2,3];

numbers.every(function(value, index, array){
  return value > 0;
});

// true
let numbers = [1,2,3];

numbers.every(function(value, index, array){
  return value > 2;
});

// false

How Does It Work?

  1. Iterates through an array
  2. Runs a callback on each value in the array
  3. If the callback returns false for any single value, return false, Otherwise, return true
function every(array, callback){
  for(let i = 0; i < array.length; i++){
    if(callback(array[i], i, array) === false){
      return false;
    }
  }
  return true;
}

How to use Every In A Function

function allIntegers(arr){
  return arr.every(Number.isInteger);
}

allIntegers([1,2,3,4,4,4,4]) // true
allIntegers([5,1,4,3,2.2]) // false

When You should Use Every

  • You need to determine if every value in an array exists and you have to determine this by using a callback
  • A simple alternative to using filter and seeing if the filtered array is of the same length as the original array

next : Learn how to use some() Method .


Previous Article
The some() Array Methods in JavaScript and how to use it .

Gopal Baskota

Full stack Web Developer

Topics

JavaScript
NodeJs
React Js

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