Array.prototype.findLast()

The Array.prototype.FindLast() method is a built-in method in JavaScript Array, which is used to find the last element in an array that satisfies the given condition. This method is similar to the Array.prototype.find() method but instead of returning the first matching element, it returns the last one.

Syntax

array.findLast(function (currentValue) {
  /**/
});
array.findLast(function (currentValue, index) {
  /**/
});
array.findLast(function (currentValue, index, arr) {
  /**/
});
array.findLast(function (currentValue, index, arr) {
  /**/
}, thisValue);

array.findLast((currentValue) => {
  /**/
});
array.findLast((currentValue, index) => {
  /**/
});
array.findLast((currentValue, index, arr) => {
  /**/
});
array.findLast((currentValue, index, arr) => {
  /**/
}, thisValue);

Parameters

The Array.prototype.FindLast() method takes two parameters:

• callback (required): It is the function that is used to test each element of the array. The function is passed three arguments:

  • currentValue: the current element being processed,
  • index: index of the current element
  • arr: on which the findLast() method was called.

• thisArg (optional): It is the value of 'this' keyword that is passed to the callback function.

return value

The Array.prototype.FindLast() method returns the value of the last element in the array that satisfies the given condition. If no element satisfies the condition, then it returns 'undefined'.

Examples

Let's take an example to understand the usage of the Array.prototype.FindLast() method:

const numbers = [2, 5, 7, 3, 8, 9];

const found = numbers.findLast((number) => number > 5);

console.log(found); // Output: 9

In this example, we have an array of numbers. We want to find the last element in the array that is greater than 5. So, we use the Array.prototype.FindLast() method and pass a callback function that checks if the number is greater than 5 or not. The method returns the value of the last element in the array that satisfies the condition, which is 9.

Now, let's take another example to understand the usage of the optional 'thisArg' parameter:

const numbers = [2, 5, 7, 3, 8, 9];

const object = {
  value: 5,
};

const found = numbers.findLast(function (number) {
  return number > this.value;
}, object);

console.log(found); // Output: 3

In this example, we have an array of numbers and an object with a 'value' property. We want to find the last element in the array that is greater than the value of the 'value' property in the object. So, we use the Array.prototype.FindLast() method and pass a callback function that checks if the number is greater than the value of the 'value' property or not. We also pass the object as the value of the 'thisArg' parameter. The method returns the value of the last element in the array that satisfies the condition, which is 3.

Notes

• The findLast() method is used to find the last element in an array that satisfies a given condition.

• The method takes a callback function as its first parameter, which is used to test each element of the array.

• The callback function takes three arguments: the current element being processed, its index, and the array on which the findLast method was called.

• The method returns the value of the last element in the array that satisfies the given condition. If no element satisfies the condition, then it returns 'undefined'.

• The findLast() method is similar to the Array.prototype.find() method but returns the last matching element instead of the first one.

• The method does not modify the original array.

• The optional 'thisArg' parameter can be used to specify the value of the 'this' keyword within the callback function.

• If the 'thisArg' parameter is not provided, the value of 'this' within the callback function will be undefined.

• The findLast() method can be used with arrays of any data type, including strings, numbers, and objects.

• The findLast() method is supported in all modern browsers, including Chrome, Firefox, Safari, and Edge.

• The method is not supported in Internet Explorer.