3 ms·

Can this model explain what "this" is in the context of an event handler? o={ f: function() setTimeout(1000,console.log(this)) } o.f() http://jsfiddle

• deleted 12y ago
  [deleted]
• zenojevski 12y ago
  The way you've written this code, `this` refers to `o`, as it has been evaluated at the time of execution of `f()` (first case) rather than inside the `setTimeout` callback, at which point it'd be `Window` (second case). So yes. Basically your code is doing this right now: o.f = function(){ console.log(this); // logs `o`, returns `undefined` setTimeout(1000, undefined); }); If you did this: o.f = function(){ setTimeout(1000, function(){ console.log(this); }); }; Then it'd be `Window` as in rule #2.
• ingenter 12y ago
  Easily. But first, let me fix some errors in your code. You probably meant to write syntactically correct code, so first line changes to following: o={ f: function() { setTimeout(1000,console.log(this)) } } Then, you probably meant to call console.log after one second, not running it immediately and passing result to timeout argument, and passing 1000 as a callback argument. So the code changes to: o={ f: function() { setTimeout(function() { console.log(this); }, 1000); } } o.f() Okay. So what happens now is that - You create and object with property 'f' - You call the function stored within that property - Within Execution Context of that function call, `this` is going to be equal to our object. Note that we have not yet used `this`. - We call setTimeout, passing it function as a callback. - After one second, that function is called, with new Execution Context, not equal to the first one. `this` there is equal to global scope variable.