Originally posted by softmoonwebware: In my case, I _rely_ on JavaScript to sort an array of HTML Elements, moving one to the top, Well, we can argue about terminology here. I would say you are _using_ JavaScript to move an element in an array. While your methology by "sorting" it gives you the result, the underlying algorithmn may change the order of other elements in the array which is an unwanted side-effect to you. Your other example of a color picker also doesn't need any server involved, because you're still _using_ JavaScript to do so. The server doesn't need to know if the client picks black or white or red or blue or any other color. Maybe the result is sent to the server, but then you cannot rely on the data to be accurate at all, because the client could send "banana" or "cat".