In the code below I expected to see the following sequence
1, 2, loaded
but I get
1, loaded, 2
Why?
<html>
<script>
window.onload = function()
{
alert('loaded');
}
(function ()
{
alert('1');
}());
(function ()
{
alert('2');
}());
</script>
<body>
</body>
</html>
In the code below I expected to see the following sequence
1, 2, loaded
but I get
1, loaded, 2
Why?
<html>
<script>
window.onload = function()
{
alert('loaded');
}
(function ()
{
alert('1');
}());
(function ()
{
alert('2');
}());
</script>
<body>
</body>
</html>
-
1
This also happens with
console.log, instead of the blockingalert: jsfiddle/9fSgE. – Felix Kling Commented May 10, 2014 at 23:43 -
2
@HalimQarroum what's the difference? It's just the way you write it, and makes more sense to execute the function
()inside it's context());and as in any language we have agreed to use the correct punctuation makes sense to do the same in JS. Same for the lost curl, it would be better to use it in the same line where the function is stated. – Roko C. Buljan Commented May 10, 2014 at 23:45 -
@FelixKling yes, I thought also that was something to do with the blocking of
alert(), seems not to be the case. Neither makes difference placing the calls inheador before</body>– Roko C. Buljan Commented May 10, 2014 at 23:49 -
Playing around a bit: If you add direct
console.logcalls between the IIFE's, you can see thatloadedis directly called after the first IIFE terminates: jsfiddle/9fSgE/1. However, if you unwrap the first IIFE, then theloadedcall appears at the very end, not after the second IIFE: jsfiddle/9fSgE/2. Unfortunately this doesn't bring me any closer to an explanation :-/ – Felix Kling Commented May 10, 2014 at 23:51 -
3
+1 Fascinating question. Can't wait for a decent explanation. Would be better updated to the
console.logversion as this, to me, is truly mystifying, whereas withalertit seems to make more sense. – spender Commented May 10, 2014 at 23:52
1 Answer
Reset to default 18You forgot ; after window onload function expression. So it bees:
window.onload = function () {
console.log('loaded');
}(function() { console.log('1'); }())
So onload function is immediately executed with a one parameter, which is a result of another IEFE. Hence
function() { console.log('1'); }()
is executed first, and immediately after that window.onload function expression. Then console.log('2') expression.
Great example why it's important not to forget semicolons at the end of the lines.