Unique identifier for HTML elements

Depending on the objective, here are two suggestions.

Unless you actually need to express the id as some kind of string, you can save the normal DOM reference.

If you do need to express it as a string for some reason, then you’ll need to assign a unique id yourself.

var getId = (function () {
  var incrementingId = 0;
  return function(element) {
    if (!element.id) {
      element.id = "id_" + incrementingId++;
      // Possibly add a check if this ID really is unique
    }
    return element.id;
  };
}());