JavaScript Tutorials

JavaScript Array every()
Syntax & Examples

Array.every() method

The every() method of the Array class in JavaScript tests whether all elements in the array pass the test implemented by the provided function. It returns a Boolean value.

Syntax of Array.every()

There are 2 variations for the syntax of Array.every() method. They are:

1.
every(callbackFn)

Parameters

ParameterOptional/RequiredDescription
callbackFnrequiredA function to test each element in the array. It takes three arguments: element, index, and array.

This method returns true if every element in the calling array satisfies the testing function.

Returns value of type Boolean.

2.
every(callbackFn, thisArg)

Parameters

ParameterOptional/RequiredDescription
callbackFnrequiredA function to test each element in the array. It takes three arguments: element, index, and array.
thisArgoptionalA value to use as this when executing callbackFn.

This method returns true if every element in the calling array satisfies the testing function, using thisArg as the value of this inside callbackFn.

Returns value of type Boolean.


✐ Examples

1 Using every() method to check if all elements are greater than a value

In JavaScript, we can use the every() method to check if all elements in an array are greater than a specified value.

For example,

  1. We define an array variable arr with elements [10, 20, 30, 40, 50].
  2. We define a callback function isGreaterThanFive to check if each element is greater than 5.
  3. We use the every() method with isGreaterThanFive to test all elements in the array.
  4. The result is stored in the variable result.
  5. We log result to the console using console.log() method to see if all elements pass the test.

JavaScript Program

const arr = [10, 20, 30, 40, 50];
const isGreaterThanFive = element => element > 5;
const result = arr.every(isGreaterThanFive);
console.log(result);

Output

true

2 Using every() method to check if all elements are strings

We can use the every() method to check if all elements in an array are strings.

For example,

  1. We define an array variable strArr with elements ['apple', 'banana', 'cherry'].
  2. We define a callback function isString to check if each element is a string.
  3. We use the every() method with isString to test all elements in the array.
  4. The result is stored in the variable result.
  5. We log result to the console using console.log() method to see if all elements pass the test.

JavaScript Program

const strArr = ['apple', 'banana', 'cherry'];
const isString = element => typeof element === 'string';
const result = strArr.every(isString);
console.log(result);

Output

true

3 Using every() method with a thisArg

We can use the every() method with a thisArg to test all elements in an array using a specific context.

For example,

  1. We define an array variable arr with elements [1, 2, 3, 4, 5].
  2. We define an object context with a threshold property set to 4.
  3. We define a callback function isLessThanThreshold to check if each element is less than the threshold property of the context object.
  4. We use the every() method with isLessThanThreshold and context as thisArg to test all elements in the array.
  5. The result is stored in the variable result.
  6. We log result to the console using console.log() method to see if all elements pass the test.

JavaScript Program

const arr = [1, 2, 3, 4, 5];
const context = { threshold: 4 };
function isLessThanThreshold(element) {
  return element < this.threshold;
}
const result = arr.every(isLessThanThreshold, context);
console.log(result);

Output

false

Summary

In this JavaScript tutorial, we learned about every() method of Array: the syntax and few working examples with output and detailed explanation for each example.