Question

I would like to create a String.replaceAll() method in JavaScript and think using a regex would be the most terse way to do it. However, I can’t figure out how to pass a variable into a regex. I can do this already which will replace all the instances of "B" with "A".

"ABABAB".replace(/B/g, "A"); 

But I want to do something like this:

String.prototype.replaceAll = function(replaceThis, withThis) {     this.replace(/replaceThis/g, withThis); }; 

But obviously, this will only replace the text "replaceThis"…so how do I pass this variable into my regex string?

Answer 1

Instead of using the /regex\d/g syntax, you can construct a new RegExp object:

var replace = "regex\\d"; var re = new RegExp(replace,"g"); 

You can dynamically create regex objects this way. Then you will do:

"mystring1".replace(re, "newstring");