**`lastIndexOf()`** is a built-in method that we can use with the `Array` type in JavaScript.

The following is the method prototype:

```javascript
Array.lastIndexOf(searchElement, fromIndex)
```

# Functionality

We use the `lastIndexOf()` method to find the position of an element in an array.

The method is similar to the `indexOf()` method, except that `lastIndexOf()` starts searching from the end of the array (unless otherwise specified) and moves backward.

# Parameters and return

The method takes the following input parameters:

- **`searchElement`:** The element to to be searched within the array.

- **`fromIndex`:** The index where the search will start. This is an optional parameter. If not otherwise specified, the search starts from the end of the array.

The `lastIndexOf` method returns the index of the last occurrence of the `searchElement`.

If the element is not found, the method returns `-1`.

// defining an array
var numbers = [12, 8, 2, 5, 12, 1, 20];

// lastIndexOf() returns the last occurance
var index1 = numbers.lastIndexOf(5);
console.log(index1); // 3

var index2 = numbers.lastIndexOf(12);
console.log(index2); // 4

// specifying starting index of search
var index3 = numbers.lastIndexOf(12, 3);
console.log(index3); // 0

// lastIndexOf returns -1 if not found
var index4 = numbers.lastIndexOf(33);
console.log(index4); // -1

What is the lastIndexOf method in JavaScript Arrays?

lastIndexOf() is a built-in method that we can use with the Array type in JavaScript. The following is the method prototype: Array.lastIndexOf(searchElement, fromIndex)  

What is the lastIndexOf method in JavaScript Arrays?

Functionality

Parameters and return

Code