Best way for $("#foo .bar")

[adrianoresende]

document.querySelector and document.querySelectorAll are quite SLOW,

What is better way if use $("#foo .bar") ?

1 - document.getElementById('foo').getElementsByClassName('bar') ?

or

2 - document.querySelector('#id .bar') ?

[kaidez]

I would say number 2 is better since getElementsByClassName is buggy. But I would also suggest that you avoid selecting things with descendant selectors as it's an anti pattern since it's under-performant.

e.g try and do document.querySelector('#id') or something similar instead of document.querySelector('#id .bar').