JavaScript .lastIndexOf()

The .lastIndexOf() array method returns the last index at which an element can be found. Otherwise, it returns -1 if the element is not found.

Syntax

array.lastIndexOf(searchElement, fromIndex);

• searchElement: The target element in the search.
• fromIndex (optional): The starting index position that search begins. The default value of fromIndex is array.length - 1. Therefore, if undefined, the search starts from the last index.

Note: A negative fromIndex will offset from the end of the array to begin the search. The array is still searched backwards.

Examples

Searching for an element not in the given array:

const fruits = ['apple', 'orange', 'peach'];

const lastIndexOfCherry = fruits.lastIndexOf('cherry');

console.log(lastIndexOfCherry);
// Output: -1

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Searching for the element indigo in an array of colors:

const rainbow = [
  'red',
  'orange',
  'yellow',
  'green',
  'blue',
  'indigo',
  'violet',
];

const checkIndigo = rainbow.lastIndexOf('indigo');

console.log(checkIndigo);
// Output: 5

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Codebyte Example

The example below defines a new array cities. The array lists the city 'Berlin' twice (multiple matches will only return the last index within the index range where a match occurs):

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