Javascript Regex LastIndex Properties

JavaScript LastIndex property helps to return the last index of the match string. We can get the regular expression pattern to match and get the last position before starting the next value. It helps with long string and array values operation and filter. The exec and test method resets the "0" value if the string does not match.

Syntax

The following syntax is used to get the last index before starting the next value.

Supported Browsers

The browsers supported by RegExp's last index properties are given below:

Google Chrome
Edge
Firefox
Internet Explorer
Opera
Safari

Examples

The following examples are the last position of the matching string.

Example 1:

The example shows the last position of the match character for the lastIndex property. Here, we use regex directly with the lastIndex keyword.

<!DOCTYPE html>
<html>
<head>
<title>
JavaScript RegExp lastIndex properties
</title>
<style>
#demo1 {
background-color: aqua;
border: 1px solid black;
width: 370px;
}
</style>
</head>

<body>
<div id = "demo1">
<h3>
JavaScript RegExp lastIndex properties
</h3>
<h4> The lastIndex property gets the Last position of the match character of the code of the function
</h4>
<!-- Click the button to get the lastIndex properties output -->
<button onclick = "display_value();"> Click Here! </button>
<div id = "regex_lastIndex"> </div>
</div>
<script>
function display_value() {
let lastIndex_value = "java javascript data jquery js";
let lastIndex_pattern = /j/g;
var final_result = "";
while (lastIndex_pattern.test(lastIndex_value)==true)  {
//Get the last position of the matching character with the lastIndex keyword
final_result += "Available lastIndex: " + lastIndex_pattern.lastIndex + "<br>";
}
//output shows " javascript" as a lastIndex
var ele_demo = document.getElementById("regex_lastIndex");
ele_demo.innerHTML = final_result;
}
</script>
</body>
</html>

Output

The output shows the last index position of the matching string.

Example 2:

The example shows the array function's last position of the matching character for the lastIndex property.

<!DOCTYPE html>
<html>
<head>
<title>
JavaScript RegExp lastIndex properties
</title>
<style>
#demo1 {
background-color: aqua;
border: 1px solid black;
width: 370px;
}
</style>
</head>
<body>
<div id = "demo1">
<h3>
JavaScript RegExp lastIndex properties
</h3>
<h4> The lastIndex property gets the Last position of the match character of the code of the function
</h4>
<!-- Click the button to get the lastIndex properties output -->
<button onclick = "display_value();"> Click Here! </button>
<div id = "regex_lastIndex"> </div>
</div>
<script>
function display_value() {
let lastIndex_value = "java, javascript data, Jquery, PHP, Js";
let lastIndex_pattern = /java/g;
var final_result = "";
while (lastIndex_pattern.test(lastIndex_value)==true)  {
//Get the last position of the matching character with the lastIndex keyword
final_result += "Available lastIndex: " + lastIndex_pattern.lastIndex + "<br>";
}
//output shows " javascript" as a lastIndex
var ele_demo = document.getElementById("regex_lastIndex");
ele_demo.innerHTML = final_result;
}
</script>
</body>
</html>

Output

The output shows the last index position of the matching string.

Example 3:

The example shows the string's last position of the match character for the lastIndex property.

<!DOCTYPE html>
<html>
<head>
<title>
JavaScript RegExp lastIndex properties
</title>
<style>
#demo1 {
background-color: aqua;
border: 1px solid black;
width: 370px;
}
</style>
</head>
<body>
<div id = "demo1">
<h3>
JavaScript RegExp lastIndex properties
</h3>
<h4> The lastIndex property gets the Last position of the match character of the code of the function
</h4>
<!-- Click the button to get the lastIndex properties output -->
<button onclick = "display_value();"> Click Here! </button>
<div id = "regex_lastIndex"> </div>
</div>
<script>
function display_value() {
let lastIndex_value = "9, 81, 19, 21, 90";
let lastIndex_pattern = /9/g;
var final_result = "";
while (lastIndex_pattern.test(lastIndex_value)==true)  {
//Get the last position of the matching character with the lastIndex keyword
final_result += "Available lastIndex: " + lastIndex_pattern.lastIndex + "<br>";
}
//output shows " javascript" as a lastIndex
var ele_demo = document.getElementById("regex_lastIndex");
ele_demo.innerHTML = final_result;
}
</script>
</body>
</html>

Output

The output shows the last index position of the matching string.

Example 4:

The example shows the number function at the last position of the matching character for the lastIndex property.

<!DOCTYPE html>
<html>
<head>
<title>
JavaScript RegExp lastIndex properties
</title>
<style>
#demo1 {
background-color: aqua;
border: 1px solid black;
width: 370px;
}
</style>
</head>
<body>
<div id = "demo1">
<h3>
JavaScript RegExp lastIndex properties
</h3>
<h4> The lastIndex property gets the Last position of the match character of the code of the function
</h4>
<!-- Click the button to get the lastIndex properties output -->
<button onclick = "display_value();"> Click Here! </button>
<div id = "regex_lastIndex"> </div>
</div>
<script>
function display_value() {
let lastIndex_value = "8, 9, 81, 19, 21, 90";
let lastIndex_pattern = /4/g;
var final_result = "";
if(lastIndex_pattern.test(lastIndex_value)==true)  {
//Get the last position of the matching character with the lastIndex keyword
final_result += "Available lastIndex: " + lastIndex_pattern.lastIndex + "<br>";
}else{
final_result += " Not Available Available lastIndex: "
}
var ele_demo = document.getElementById("regex_lastIndex");
ele_demo.innerHTML = final_result;
}
</script>
</body>
</html>

Output

The output shows the last index position of the matching string.