A RegExp constructor is used to create a new regular expression object containing a search pattern.

The first argument is a string containing a properly escaped pattern. Because the backslash character (\) is an escape when used in a string, for the back slashes to remain in the regular expression pattern, they will need to be double escaped. For example, this pattern:

/\d+/

Must be escaped like this when used in a string:

"\\d+"

The second argument is the attributes for the pattern. You should not put the attributes on the end of the pattern but specify them separately. These are available:

The regular expression constructor is useful for those occasions when you cannot easily predict what string you will need to match. If you could, it is likely you would use a regular expression literal. If the user is going to enter some value that determines what the search characteristics are to be then a RegExp() constructor may be useful.

Example code:

   // Declare a variable and assign a RegExp literal to it

   var myPattern = /x$/;

   // Now do the same thing with a RegExp constructor

   var myPattern = new RegExp("x$");

Cross-references:

ECMA 262 edition 3 - section - 15.10.4