The Array.prototype.lastIndexOf() method in TypeScript is used to find the last index at which a given element can be found in the array, searching backwards from the fromIndex. It returns the index of the found element, or -1 if the element is not present.
Syntax:
array.lastIndexOf(searchElement[, fromIndex])Parameter: This method accepts two parameter as mentioned above and described below:
- searchElement : This parameter is the element to locate in the array.
- fromIndex : This parameter is the index at which to start searching backwards.
Return Value: This method returns the index of the found element from the last.
Below examples illustrate the Array lastIndexOf() method in TypeScript.
Examples of Array lastIndexOf() Method
Example 1: Basic Usage of lastIndexOf()
In this example, we will demonstrate the basic usage of the lastIndexOf() method to find the last occurrence of an element in an array.
const arr: number[] = [1, 2, 3, 2, 1];
const index: number = arr.lastIndexOf(2);
console.log(index);
Output:
3
Example 2:
const arr: number[] = [1, 2, 3, 2, 1];
const index1: number = arr.lastIndexOf(2, 4);
console.log(index1);
const index2: number = arr.lastIndexOf(2, 2);
console.log(index2);
const index3: number = arr.lastIndexOf(3, 4);
console.log(index3);
Output:
3
1 2