Understanding javascript closure

Question

function makeHelpCallback(help) {
  return function() {
    showHelp(help);
  };

//array elements here

  for (var i = 0; i < helpText.length; i++) {
    var item = helpText[i];
    document.getElementById(item.id).onfocus = makeHelpCallback(item.help);
}

I am having trouble understanding the last line. I have never seen the equal sign used in that way,

It's like `element.onclick = function() { alert(); }`, it's just an element with an event on one side, and a function call on the other. — adeneo, Feb 27 '13 at 21:10
That whole block is invalid... You are missing a `}` somewhere... — Naftali, Feb 27 '13 at 21:10
Where is the closing brace `}`? I'm assuming before the "array elements here" comment? — Austin Mullins, Feb 27 '13 at 21:11
Regarding why a closure is needed here, see http://stackoverflow.com/questions/1451009/javascript-infamous-loop-problem — bfavaretto, Feb 27 '13 at 21:13
possible duplicate of [How do JavaScript closures work?](http://stackoverflow.com/questions/111102/how-do-javascript-closures-work) — CassOnMars, Feb 27 '13 at 21:25
@insertusernamehere Yes, there is. See the two questions linked from the comments. — bfavaretto, Feb 27 '13 at 21:35

score 6 · Answer 1 · answered Feb 27 '13 at 21:10

6

I have never seen the equal sign used in that way

It assigns the return value of a function call (another function in this case; they are first class objects so can be passed around) to a property of an object.

answered Feb 27 '13 at 21:10

Quentin

914,110
126
1,211
1,335

Thanks everyone and especially Quentin, I think i get it. – user2117138 Feb 28 '13 at 17:59

Understanding javascript closure

1 Answers1