Editing querySelectorAll class names vs attributes 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) Curious to see if there is any perf diff between querySelectorAll('.cat.bobtail') and querySelectorAll('[data-cat="bobtail"]'), because I would rather use more meaningful data- attribute than some arbitrary class names. 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> <div id="sektion"> </div> <script> var f = document.createDocumentFragment(), div, sektion = document.getElementById('sektion'); for (var i = 0; i < 500; i++) { div = document.createElement('div'); div.className = 'foo bar'+i; div.setAttribute('sekt','bar'+i); f.appendChild(div); }; sektion.appendChild(f); </script> 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) Code snippets to compare Test 1 Title Async (check if this is an asynchronous test) Code document.querySelectorAll('.foo'); Test 2 Title Async (check if this is an asynchronous test) Code document.querySelectorAll('[class~="foo"]'); Test 3 Title Async (check if this is an asynchronous test) Code document.querySelectorAll('[class~=bar1],[class~=bar2],[class~=bar3]'); Test 4 Title Async (check if this is an asynchronous test) Code document.querySelectorAll('.bar1,.bar2,.bar3'); Test 5 Title Async (check if this is an asynchronous test) Code document.querySelectorAll('[sekt^=bar]'); // same as .foo Test 6 Title Async (check if this is an asynchronous test) Code jQuery('.bar1,.bar2,.bar3'); Test 7 Title Async (check if this is an asynchronous test) Code jQuery('[class~=bar1],[class~=bar2],[class~=bar3]'); Test 8 Title Async (check if this is an asynchronous test) Code jQuery('[class~=bar1]').add('[class~=bar2]').add('[class~=bar3]'); Test 9 Title Async (check if this is an asynchronous test) Code jQuery('[class~=bar1]').add('[class~=bar2],[class~=bar3]'); Test 10 Title Async (check if this is an asynchronous test) Code document.querySelectorAll('[sekt=bar1],[sekt=bar2],[sekt=bar3]'); Test 11 Title Async (check if this is an asynchronous test) Code jQuery('[sekt=bar1],[sekt=bar2],[sekt=bar3]');