How to create regular expression with RegExp constructor

Description

Regular expressions can be created by using the RegExp constructor, which accepts two arguments:

• a string pattern to match and
• an optional string of flags to apply.

Example

// Match the first instance of "bat" or "cat", regardless of case.
var pattern1 = /at/i;
/*from   w ww.  j av a2  s .  co m*/
// Same as pattern1, using the constructor.
var pattern2 = new RegExp("at", "i");

Note

Double-escape are needed for RegExp constructor since it accepts string as parameter.

The following table compares patterns in literal form and cooresponding form in the RegExp constructor.