To get the square root, use the Math.sqrt() method. This method returns the square root of a number. If the value of a number is negative, sqrt returns NaN.
Example
You can try to run the following code to get the square root of a number −
<html>
<head>
<title>JavaScript Math sqrt() Method</title>
</head>
<body>
<script>
var value = Math.sqrt( 0.5 );
document.write("First Value : " + value );
var value = Math.sqrt( 49 );
document.write("<br />Second Value : " + value );
</script>
</body>
</html>