Javascript LastIndexOf() Function

The join() function of array object will returns the last index of an element within the array equal to the specified value, or -1 if none is found. Use it for example to start searching backwards.

Syntax

arr.lastIndexOf(searchElement[, fromIndex])

Javascript LastIndexOf() Function Example1

<html>
<head>
<script type="text/javascript">
// Create an array.
var arr = ['Jan', 'Fab', 'Mar', 'April', 'Jan'];
// Determine the first location, in descending order, of "Jan".
document.write(arr.lastIndexOf("Jan") + "<br/>");

// Find "Jan" in descending order, starting at index 2.
document.write(arr.lastIndexOf("Jan", 2) + "<br/>");

// Search for "May" (which is not found).
document.write(arr.lastIndexOf("May")+ "<br/>");
</script>
</head>
<body>
</body>
</html>

This will produce following result

4
1
-1

Javascript LastIndexOf() Function Example2

<html>
<head>
<script type="text/javascript">
// Create an array.
var arr = [1,2,3,4,5,6,7,1,2];

document.write(arr.lastIndexOf(1) + "<br/>");
document.write(arr.lastIndexOf(2) + "<br/>");
</script>
</head>
<body>
</body>
</html>

This will produce following result