Javascript - Add to a RegEx

Question

I'm working with a library which specifies a RegEx on an object. I need to add some characters into that RegEx. Is there a less hacky way of doing this?

I have no control over this.stripCharsRegex.

// this.stripCharsRegex =   /[^0123456789.-]/gi
var regexChars = this.stripCharsRegex.toString();
regexChars = regexChars.substr(3,regex.length-7);  // remove '/[^'  and   ']/gi'
var regex = new RegExp('[^£$€'+regexChars+']','gi');  // (e.g.)
this.stripCharsRegex = regex;

Answer 1

I think you should be able to combine new regexp rule with old RegExp object if you use its source property. Try this:

this.stripCharsRegex = new RegExp('(?=[^£$€])' + this.stripCharsRegex.source, 'gi');

Check test snippet below.

var stripCharsRegex = new RegExp('[^0123456789.-]', 'gi');

alert( 'Total: $123 test - £80&dd'.replace(stripCharsRegex, '') );

// extend regexp by creating new RegExp object
stripCharsRegex = new RegExp('(?=[^£$€])' + stripCharsRegex.source, 'gi');

alert( 'Total: $123 test - £80&dd'.replace(stripCharsRegex, '') );