A regular expression is an object that describes a pattern of characters. The JavaScript RegExp class represents regular expressions, and both String and RegExp define methods that use regular expressions to perform powerful pattern-matching and search-and-replace functions on the text.
A regular expression could be defined with the RegExp () constructor, as follows −
var pattern = new RegExp(pattern, attributes); or simply var pattern = /pattern/attributes;
The following are the parameters −
- pattern − A string that specifies the pattern of the regular expression or another regular expression.
- attributes − An optional string containing any of the "g", "i", and "m" attributes that specify global, case-insensitive, and multiline matches, respectively.
Example
You can try to run the following code to learn how to implement RegExp object in JavaScript −
<html>
<head>
<title>JavaScript RegExp</title>
</head>
<body>
<script>
var re = new RegExp( "string" );
document.write("re.constructor is:" + re.constructor);
</script>
</body>
</html>