Editing querySelectorAll vs getElementsByTagName vs getElementsByClassName vs jQuery This edit will create a new revision. Your details (optional) Name Email (won’t be displayed; might be used for Gravatar) URL Test case details Title * Published (uncheck if you want to fiddle around before making the page public) Description (in case you feel further explanation is needed)(Markdown syntax is allowed) Checking how querySelectorAll('parent child') or '.parent .child' selection performs against combinations of getElementsByTagName, getElementsByClassName, jQuery. On the jQuery part, it is tested in two ways: .root-ul is a class that defines a single node. So it might be interesting to check if this allows some speed boost. Are you a spammer? (just answer the question) Preparation code Preparation code HTML (this will be inserted in the <body> of a valid HTML5 document in standards mode) (useful when testing DOM operations or including libraries) <script src="//ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"></script> <ul class="root-ul"><li><a class="link word" href="#word">word</a> </li><li><a class="link glass" href="#glass">glass</a> </li><li><a class="link lorum" href="#lorum">lorum</a> </li><li><a class="link ipsum" href="#ipsum">ipsum</a> </li><li><a class="link dolor" href="#dolor">dolor</a> </li><li><a class="link sit-amet" href="#sit-amet">sit-amet</a> </li></ul> Include JavaScript libraries as follows: <script src="//cdn.ext/library.js"></script> Define setup for all tests (variables, functions, arrays or other objects that will be used in the tests) (runs before each clocked test loop, outside of the timed code region) (e.g. define local test variables, reset global variables, clear canvas, etc.) (see FAQ) Define teardown for all tests (runs after each clocked test loop, outside of the timed code region) (see FAQ) window.console && console.log && nodes.length != 6 && console.log('nodes:',nodes.length, nodes); Code snippets to compare Test 1 Title Async (check if this is an asynchronous test) Code var root = document.querySelectorAll('ul .link'), nodes = [], l, i; for (i = 0, l = root.length; i < l; i++) { nodes.push(root[i]); } Test 2 Title Async (check if this is an asynchronous test) Code var root = document.querySelectorAll('ul .link'), nodes = [], l, i, push = Array.prototype.push; for (i = 0, l = nodes.length = root.length; i < l; i++) { push.apply(nodes, root[i]); } Test 3 Title Async (check if this is an asynchronous test) Code var root = document.getElementsByClassName('root-ul'), nodes = [], l, i, push = Array.prototype.push; for (i = 0, l = root.length; i < l; i++) { push.apply(nodes, root[i].getElementsByClassName('link')); } Test 4 Title Async (check if this is an asynchronous test) Code var root = document.getElementsByClassName('root-ul'), nodes = [], l, i, push = Array.prototype.push; for (i = 0, l = root.length; i < l; i++) { push.apply(nodes, root[i].getElementsByTagName('a')); } Test 5 Title Async (check if this is an asynchronous test) Code var root = document.getElementsByClassName('link'), nodes = [], l, i, push = Array.prototype.push; for (i = 0, l = nodes.length = root.length; i < l; i++) { push.apply(nodes, root[i]); } Test 6 Title Async (check if this is an asynchronous test) Code var root = document.getElementsByClassName('link'), nodes = [], l, i, push = Array.prototype.push; for (i = 0, l = nodes.length = root.length; i < l; i++) { push.apply(nodes, root[i]); } Test 7 Title Async (check if this is an asynchronous test) Code var nodes = jQuery('.root-ul .link'); Test 8 Title Async (check if this is an asynchronous test) Code var nodes = jQuery('.root-ul').find('.link');