Javascript strange loading sequence

Question

In the code below I expected to see the following sequence

1, 2, loaded 

but I get

1, loaded, 2

Why?

Answer 1

You forgot ; after window onload function expression. So it becomes:

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.