Insert a string into an existing RegExp in Javascript?

Question

Possible Duplicate:
passing variable to a regexp in javascript

I have a variable:

resource = "user";

I want to insert that variable into a predefined RegExp (replacing variable beneath):

/^\/variable\/\d+$/

How could I do that?

Answer 1

You should be able to do this.

var resource = "user";
var regex = new RegExp("^\/"+resource+"\/\d+$", "g");

You can then pass the RegExp object to functions like myString.replace() or call the exec() method of the RegExp object itself.

Answer 2

You can use the new RegExp method:

var resource = "user";
new RegExp("^\/"+variable+"\/\d+$");

Answer 3

Use the constructor of RegExp:

var re = new RegExp("^\\/" + resource + "\\/\\d+$");

Note that you need to escape the delimiters / twice, once for the regular expression and once for the string declaration.

You also might want to use some escape function to quote strings to be used in regular expressions:

function quote(str) {
    return str.replace(/(?=[\/\\^$*+?.()|{}[\]])/g, "\\");
}

That leads us to this:

var re = new RegExp("^\\/" + quote(resource) + "\\/\\d+$");