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

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— 

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.

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