JavaScript Array every() Tutorial

In this section, we will learn what the every() method is and how to use it in JavaScript.

JavaScript Arrays every() Method

The `every()` method is used to run a test on every element in an array. Basically, when we want to exam all the elements in an array, we can use this method.

Array every() Syntax:

array.every(function(currentValue, index, arr), thisValue)

Array every() Method Parameters:

The `every()` method takes two arguments.

The first argument is a reference to a function. For each element in the target array, the `every()` method will call that function.

For each call to this function, three arguments will be passed as well:

  • The first argument is the element of the array that the function is called for.
  • The second argument is the index number of this element.
  • The third argument is a reference to the target array itself.

Inside this function we define a set of instructions to exam each element and at the end, this function should return either the value `true` or `false` as a result of the examination.

Other than the function, the `every()` method takes a second argument as well. This second argument, which is optional, is a reference to an object that will bind to the `this` keyword in the target function that we passed as the first argument.

Array every() Method Return Value:

The final result of the `every()` method is a Boolean value. If the result of all the elements in the function was `true`, the final result of the `every()` method becomes also `true`. Otherwise, even if the result of calling the function for one element returned `false` the final result for the `every()` method will be `false` as well.

Example: Checking All Elements in JavaScript Array

const arr = ["Tesla","Google","Microsoft","Amazon","Facebook","Twitter"];
function eve(value, index, arr){
  return typeof value =="string"?true: false; 
}

const final = arr.every(eve);
console.log(final);

Output:

true

Example: using JavaScript every() method in JavaScript

const arr = ["Tesla","Google","Microsoft",2,3,4,"Amazon","Facebook","Twitter"];
function eve(value, index, arr){
  return typeof value =="string"?true: false; 
}

const final = arr.every(eve);
console.log(final);

Output:

false

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