Question

As said here:

http://jqfundamentals.com/book/index.html

Closures can also be used to resolve issues with the this keyword,
which is unique to each scope. This
mechanism can be particularly useful
when dealing with callbacks, though in
those cases, it is often better to use
Function.bind, which will avoid any
overhead associated with scope
traversal.

But it doesn’t really say how to distinguish between the two cases. I don’t understand in fact what the author means by "avoid any overhead associated with scope traversal." Can you explain?

Answer 1

Take a look at this line in the example in the link above

console.log(self.myName, this.myName);

(with self = this; a couple of lines above). The closure defined outerFunction method, exists in a different scope that is why it has a different this value from the outerObj object. (self.myName!=this.myName)

Scope traversal means, when you are reaching to grab a value (variable,object) that exists in a different scope, therefore additional overhead is added (code becomes slower to execute).

Using bind, you ‘re calling a function with an existing scope, so that scope traversal does not take place.