JavaScript Tutorials

JavaScript Array findLast()
Syntax & Examples

Array.findLast() method

The findLast() method of the Array class in JavaScript returns the value of the last element in the array that satisfies the provided testing function. If no element satisfies the testing function, undefined is returned.

Syntax of Array.findLast()

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

1.
findLast(callbackFn)

Parameters

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

This method returns the value of the last element in the array that satisfies the provided testing function.

Returns value of type Any.

2.
findLast(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 the value of the last element in the array that satisfies the provided testing function, using thisArg as the value of this inside callbackFn.

Returns value of type Any.


✐ Examples

1 Using findLast() method to find the last even number

In JavaScript, we can use the findLast() method to find the last even number in an array.

For example,

  1. We define an array variable arr with elements [1, 3, 7, 8, 10].
  2. We define a callback function isEven to check if each element is an even number.
  3. We use the findLast() method with isEven to find the last even number in the array.
  4. The result is stored in the variable lastEven.
  5. We log lastEven to the console using console.log() method to see the found element.

JavaScript Program

const arr = [1, 3, 7, 8, 10];
const isEven = element => element % 2 === 0;
const lastEven = arr.findLast(isEven);
console.log(lastEven);

Output

10

2 Using findLast() method to find the last string with length greater than 3

We can use the findLast() method to find the last string with length greater than 3 in an array.

For example,

  1. We define an array variable strArr with elements ['a', 'bc', 'def', 'ghij'].
  2. We define a callback function isLengthGreaterThanThree to check if the length of each string is greater than 3.
  3. We use the findLast() method with isLengthGreaterThanThree to find the last string with length greater than 3 in the array.
  4. The result is stored in the variable lastLongString.
  5. We log lastLongString to the console using console.log() method to see the found element.

JavaScript Program

const strArr = ['a', 'bc', 'def', 'ghij'];
const isLengthGreaterThanThree = element => element.length > 3;
const lastLongString = strArr.findLast(isLengthGreaterThanThree);
console.log(lastLongString);

Output

ghij

3 Using findLast() method with a thisArg

We can use the findLast() method with a thisArg to find the last element in an array using a specific context.

For example,

  1. We define an array variable arr with elements [5, 12, 8, 130, 44].
  2. We define an object context with a threshold property set to 10.
  3. We define a callback function isGreaterThanThreshold to check if each element is greater than the threshold property of the context object.
  4. We use the findLast() method with isGreaterThanThreshold and context as thisArg to find the last element greater than the threshold.
  5. The result is stored in the variable foundElement.
  6. We log foundElement to the console using console.log() method to see the found element.

JavaScript Program

const arr = [5, 12, 8, 130, 44];
const context = { threshold: 10 };
function isGreaterThanThreshold(element) {
  return element > this.threshold;
}
const foundElement = arr.findLast(isGreaterThanThreshold, context);
console.log(foundElement);

Output

44

Summary

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