chaining getElementById

Question

I\'ve been looking for an answer to this question but I could find none so I thought I\'d try StackOverflow.

In javascript, is this valid:

x = document

Answer 1

This is a fast alternative based on Node.contains

var getById = function(id, context) {
  var el = document.getElementById(id);
  return context.contains(el) ? el : null;
}

var container = document.getElementById('container-element');
getById('my-element-id', container);

The last line (profiled on latest Chrome and Firefox) performs 4x to 10x faster than jQuery's equivalent

$('#my-element-id', container);

The only good alternative is querySelector (a bit faster)

container.querySelector('#my-element-id');