JavaScript Array findLastIndex()
Example 1
Find the last element with a value over 18:
const ages = [3, 10, 18, 20];
ages.findLastIndex(checkAge);
function checkAge(age) {
return age > 18;
}
Try it Yourself »
ages.findLastIndex(checkAge);
function checkAge(age) {
return age > 18;
}
Description
The findLastIndex() method executes a function for each array element.
The findLastIndex() method returns the index (position) of the last element that passes a test.
The findLastIndex() method returns -1 if no match is found.
The findLastIndex() method does not execute the function for empty array elements.
The findLastIndex() method does not change the original array.
Array Find Methods:
| Method | Finds |
|---|---|
| includes() | Returns true if an array contains a specified value |
| indexOf() | The index of the first element with a specified value |
| lastIndexOf() | The index of the last element with a specified value |
| find() | The value of the first element that passes a test |
| findIndex() | The index of the first element that passes a test |
| findLast() | The value of the last element that passes a test |
| findLastIndex() | The index of the last element that passes a test |
Syntax
array.findLastIndex(function(currentValue, index, arr), thisValue)
Parameters
Parameter
Description
function()
Required.
A function to be run for each array element.
A function to be run for each array element.
currentValue
Required.
The value of the current element.
The value of the current element.
index
Optional.
The index of the current element.
The index of the current element.
arr
Optional.
The array of the current element.
The array of the current element.
thisValue
Optional. Default
A value passed to the function as its
undefined.A value passed to the function as its
this value.
Return Value
Type
Description
Number
The index of the last element that passes the test.
Otherwise -1.
Otherwise -1.
More Examples
Find the last element with a value above an input value:
<p><input type="number" id="toCheck" value="18"></p>
<button onclick="myFunction()">Test</button>
<p>Any values above: <span id="demo"></span></p>
<script>
const numbers = [4, 12, 16, 20];
function checkValue(x) {
return x > document.getElementById("toCheck").value;
}
function myFunction() {
document.getElementById("demo").innerHTML = numbers.findLastIndex(checkValue);
}
</script>
Try it Yourself »
<button onclick="myFunction()">Test</button>
<p>Any values above: <span id="demo"></span></p>
<script>
const numbers = [4, 12, 16, 20];
function checkValue(x) {
return x > document.getElementById("toCheck").value;
}
function myFunction() {
document.getElementById("demo").innerHTML = numbers.findLastIndex(checkValue);
}
</script>
Array Tutorials:
Browser Support
findLastIndex() is a JavaScript 2023 feature.
ES 2023 is supported in all modern browsers since July 2023:
| Chrome 110 |
Edge 110 |
Firefox 115 |
Safari 16.4 |
Opera 96 |
| Feb 2023 | Feb 2023 | Jul 2023 | Mar 2023 | May 2023 |