javascript multi-replace

multi_replace.js

var str = "/activity_sets/:activity_set_id/activity_set_annotations/:id/edit John Smith"
  , repl = {
      "11": ":activity_set_id",
      "1": ":id",
      "$2, $1": new RegExp("(John)\\s(Smith)", "gi")
  };

function multi_replace(str, repl) {
  if (!str) return str;

  if (typeof repl != "object") return str;

  for (r in repl) {
    var pattern = repl[r];
    if (Object.prototype.toString.call(pattern) != "[object RegExp]") pattern = new RegExp(pattern);
    str = str.replace(pattern, r);
  }

  return str;
}

var s = multi_replace(str, repl);
console.log(s); // /activity_sets/11/activity_set_annotations/1/edit Smith, John