JavaScript RegExp in replace() not working

Question

I have this code

var str = "Some text :$0";
var i = 0;

alert(str.replace(new RegExp("\:\$" + i, "g"), 'here'));

see here.

Why is it not working? If I do it like this /\:\$:0/g instead of using the RegExp object then it works but I can't use a variable in the pattern that way. Whats wrong?

Answer 1

Because in string literals, \ has a special meaning. If you want to actually put a \ in the regular expression, you need to escape it in the string literal:

new RegExp("\\:\\$" + i, "g")

But : has no special meaning in regular expressions, no need to escape it:

new RegExp(":\\$" + i, "g")

var str = "Some text :$0";
var i = 0;

console.log(str.replace(new RegExp(":\\$" + i, "g"), 'here'));