Why assign `this` to `self` and run `self.method()`?

Question

I'm reading the source from mongoose

Collection.prototype.onOpen = function () {
  var self = this;
  this.buffer = false;
  self.doQueue();
};

I don't understand why the author assigns this to self and runs self.doQueue(). Why not just run:

this.buffer = false;
this.doQueue();

I'm new to javascript, thanks for help.

Answer 1

You're right, in this instance they could have simply used this.

The use of me or self is a bit of a hack to ensure the correct context of this is used, as within JavaScript the scope of this is variant. If for example you have an event trigger a function within your class, this would be different, and wouldn't be your object that houses the function, but instead the object that called the function. To resolve this people often use me or self to ensure they're referring to the correct object... this, as in the actual object.