# findLastIndex method

The `findLastIndex` method helps to find the index of the first element from the end of an array that matches the condition according to the callback parameter. If there is no element, then `-1` is returned.

## Syntax

`array.findLastIndex(function);`

## Example

Let's find the index of a positive number in an array:

`let arr = [-12, -13, 14, 15]; let res = arr.findLastIndex(function(elem) { return elem > 0; }); console.log(res);`

The code execution result:

`3`

## Example

And now let's find the index of an element that is not in an array:

`let arr = ['a', 'b', 'c', 'd']; let res = arr.findLastIndex(function(elem) { return elem === 'f'; }); console.log(res);`

The code execution result:

`-1`

## See also

- the `find` method
  that searches for an element in an array
- the `findIndex` method
  that searches for the index of an element in an array
- the `findLast` method
  that searches for an element from the end of an array

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