w3resource

JavaScript lastIndexOf() Method: String Object

Description

The lastIndexOf() method returns the index within the calling string object of the last occurrence of the specified value. It returns -1 if not found. The calling string is search in reverse order, starting at startIndex.

Version

Implemented in JavaScript 1.0

Syntax

lastIndexOf(searchValue, startIndex) 

Parameter

searchValue :  A string representing the value to search for.

startIndex  : The location in the string to search the specified value. Location value is an integer between 0 and the length of the string. The default value is 0.

Example:

In the following web document lastIndexOf() method is used to locate values in a given string.

"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<meta http-equiv="content-type" content="text/html; charset=iso-8859-1" />
<title>JavaScript String object - lastIndexOf() method example</title>
</head>
<body>
<h1 style="color: red">JavaScript String object : lastIndexOf() method</h1>
<hr />
<script type="text/javascript">
//This is done to make the following JavaScript code compatible to XHTML. <![CDATA[
var str="Learn Javascript";
document.write(str.lastIndexOf("Learn") + "<br />");
document.write(str.lastIndexOf("Javascript")+"<br />");
document.write(str.lastIndexOf("Easily"));
//]]>
</script>
</body>
</html>

View the example in the browser

Supported Browser

Internet Explorer 7 Firefox 3.6 Google Chrome 7 Safari 5.0.1 Opera 10
Yes Yes Yes Yes Yes

See also:

JavaScript Core objects, methods, properties.

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JavaScript: Tips of the Day

How to check whether a string contains a substring in JavaScript?

ECMAScript 6 introduced String.prototype.includes:

const string = "foo";
const substring = "oo";

console.log(string.includes(substring));

includes doesn't have Internet Explorer support, though. In ECMAScript 5 or older environments, use String.prototype.indexOf, which returns -1 when a substring cannot be found:

var string = "foo";
var substring = "oo";

console.log(string.indexOf(substring) !== -1);

Ref: https://bit.ly/3fFFgZv