Question

In my application,I use many setTimeout function,so I am afraid if it will cause peformance problem:

setTimeout(function(){
  // do something
},0);

And I found people use this manner:

var t=setTimeout(function(){
  // do something
  clearTimeout(t);
});

I wonder if it is necessary?

Answer 1

No, object will be destroyed automatically (at least should be). You need to call clearTimeout when you need to remove already set timeout.

Ex: you have set timeout to 5 seconds on hovering some element but user moves out cursor from element before timeout elapsed – so you need to remove already initialized timeout.