How to useRegExp in Javascript

Approach 1: Using parseInt() Method

The RegExp is used to replace the ‘px’ with an empty string and then convert the result to Integer using Number() method.

Example: This example implements the above approach.

html

<!DOCTYPE html>
<html lang="en">
 
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content=
        "width=device-width, initial-scale=1.0">
 
    <title>
        How to convert a pixel value to a 
        number value using JavaScript ?
    </title>
</head>
 
<body>
    <h1 style="color:green;">
        w3wiki
    </h1>
 
    <p id="checkFontSize" style="font-size: 19px">
        Click on Button to get this 
        font size value in number
    </p>
 
    <button onclick="GFG_Fun()">
        Click Here
    </button>
 
    <p id="result"></p>
 
    <script>
        const str = document.getElementById("checkFontSize");
 
        const res = document.getElementById("result");
 
        const fontSizePX = str.style.fontSize;
 
        function GFG_Fun() {
            res.innerHTML = "Integer value is " + 
                Number(fontSizePX.replace(/px$/, ''));
        }
    </script>
</body>
 
</html>