Lookbehind Assertions JavaScript Regular Expressions

JavascriptWeb DevelopmentObject Oriented Programming

Lookbehind allows matching a pattern only if there’re something before.Following is an example −

Example

 Live Demo

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>Document</title>
<style>
   body {
      font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
   }
   .sample, .result {
      font-size: 20px;
      font-weight: 500;
   }
</style>
</head>
<body>
<h1>Look behind Assertions Regular Expressions</h1>
<div class="sample">The price for 4 tables are $50 , $99 , $121 and $150.</div>
<div style="color: green;" class="result"></div>
<button class="btn">CLICK HERE</button>
<h3>
Click on the above button to extract the table price using lookbehind
</h3>
<script>
   let sampleEle = document.querySelector(".sample").innerHTML;
   let btnEle = document.querySelector(".btn");
   let resEle = document.querySelector(".result");
   const priceRegex=/(?<=\$)\d+/g;
   btnEle.addEventListener("click", () => {
      resEle.innerHTML = "Table price are = "+sampleEle.match(priceRegex);
   });
</script>
</body>
</html>

Output

The above code will produce the following output −

On clicking the ‘CLICK HERE’ button −

raja
Published on 15-Jul-2020 16:27:57
Advertisements