Message from JavaScript discussions

September 2018

— For asynchronous functions where you don't control when the function is done, you can pass the callback, and it will be called when it's done

Message permanent page


asyncFunction(param1, param2, callback)
// someOtherStuff...

asyncFunction is called, but you don't wait for it to complete. someOtherStuff continues to happen, and whenever asyncFunction is done running, it will call callback which is also a function

— Does that make sense Adan?

— Thank you

— No, querySelectorAll obviously does more work

— ?

— Where is the test?

— It may do more work, but getElementsByClassName may be doing even more work🤤

— ClassName takes a class name, querySelector takes a query, which it has to parse

— To find potentially classnames, potentially other stuff

— And THEN it executes what it parsed

— But still htmlcollection updates itself when any dom node with the corresponding classname gets added later on. Maybe elementsByClassName is initially faster but I still think queryselctorall is overall faster. And when you just use querySelectorAll(".foo") instead of getElementsByClassName("foo") it shouldnt be a real performance difference. In the jsperf test it was supposed to be way faster.

Message permanent page