The RegExp Object

As mentioned at the beginning of this chapter, regular expressions are represented as RegExp objects. In addition to the RegExp() constructor, RegExp objects support three methods and a number of properties. RegExp pattern-matching methods and properties are described in the next two sections.

The RegExp() constructor takes one or two string arguments and creates a new RegExp object. The first argument to this constructor is a string that contains the body of the regular expression—the text that would appear within slashes in a regular-expression literal. Note that both string literals and regular expressions use the \ character for escape sequences, so when you pass a regular expression to RegExp() as a string literal, you must replace each \ character with \\. The second argument to RegExp() is optional. If supplied, it indicates the regular-expression flags. It should be g, i, m, or a combination of those letters.

For example:

// Find all five-digit numbers in a string. Note the double \\ in this case.
var zipcode = new RegExp("\\d{5}", "g");

The RegExp() constructor is useful when a regular expression is being dynamically created and thus cannot be represented with the regular-expression literal syntax. For example, to search for a string entered by the user, a regular expression must be created at runtime with RegExp().

RegExp Properties

Each RegExp object has five properties. The source property is a read-only string that contains the text of the regular expression. ...

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