This method causes a string to be displayed in the specified size as if it were in a <font size= "size"> tag.
Example
You can try to run the following code to change the font size of a text using JavaScript −
<html>
<head>
<title>JavaScript String fontsize() Method</title>
</head>
<body>
<script>
var str = new String("Demo Text");
document.write(str.fontsize(10));
alert(str.fontsize( 10 ));
</script>
</body>
</html>