在setTimeout中调用Javascript函数-哪个更好？

Question

I have two versions of the code. Can someone let me know which is optimal and faster?

Version 1:

function showMsg(a)
{
    alert(a);
}
function invokeShowMsg()
{
    var msg = 'hi';
    showMsg(msg);
}
window.setTimeout(invokeShowMsg,1000);

Version 2:

function showMsg(a)
{
    alert(a);
}
window.setTimeout(function(){showMsg('hi');},1000);

One more doubt, is the Version 2 way of calling called "Closure"?

Answer 1

As far as speed goes, you will not notice any difference between the two whatsoever, so pick what you like.

I prefer #2 , as it is cleaner and keeps the syntax readable:

setTimeout(function() {
  showMsg('hi');
}, 1000);

Answer 2

Yes , version 2 is called Closure. As far as speed, they are both equivalent.

Answer 3

As @Blender said, I also prefer 2 , as it doesn't pollute the global space with (semi-useless) "caller" functions. It's clean, and it simple to understand to someone who knows how setTimeout works. And as far as speed goes, there's virtually no difference. Here's a performance comparison of the two methods .

However, as far as I understand, it is not a closure. It is simply an anonymous function. In JavaScript, as in many other dynamic language, functions are first class citizens , meaning that they can be created and passed around- they are objects. However, a closure is more than just an anonymous function. The answers to this question explain what a closure is quite succinctly.