Dynamic Replacement of string parameters

gistfile1.js

//replaces a string's commas with spaces
var replacement = 'test';

//in my use i had a for loop that used the index to generate the value 
//in this example if you had it in a loop it would replace each '$NUMBER' with 'test'
for(var i=0; i<5; i++){
  final = final.split('$'+value).join(replacement);
}