JavaScript lastIndex Property

The lastIndex property in JavaScript returns the index position when a match occurs and the next match then resumes from that position only. The lastIndex property works only if the ‘g’ modifier is set.

Following is the code for the lastIndex property in JavaScript −


 Live Demo

<!DOCTYPE html>
<html lang="en">
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
   body {
      font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
   .result {
      font-size: 18px;
      font-weight: 500;
      color: red;
<h1>JavaScript lastIndex Property</h1>
<div class="sample">The king bought an expensive ring.</div>
<div style="font-weight: bold; color: black;" class="result"></div>
<button class="Btn">CLICK HERE</button>
Click on the above button to find the index of 'ing' in the above string
   let sampleEle = document.querySelector(".sample");
   let resultEle = document.querySelector(".result");
   let regex = new RegExp("ing", "g");
   document.querySelector(".Btn").addEventListener("click", () => {
      resultEle.innerHTML +='"ing" found Current Index = ' + regex.lastIndex + "<br>";
      resultEle.innerHTML += '"ing" found Current Index = ' + regex.lastIndex;


On clicking the ‘CLICK HERE’ button −