Section 11- Closures and the Keyword this

Section Slides

this Keyword

Four Rules for determining

1. Global Context

   when this is not inside of a declared object its value is the 'window' object (in browser)

   when "use strict"/strict mode this when inside a function or when a variable is declare inside a function it is undefined in the global obj.

2. Implicit/Declared in Object

   When this is inside of a declared object its value is the closest parent object

3. Explicit Binding

   • call -> immediately invoked -> fn.call(thisArg,a,b,c...)
   • apply -> immediately invoked -> fn.apply(thisArg,[a,b,c...])
   • bind -> returns a function def -> fn.bind(thisArg,a,b,c,d...)-> useful when using asynchronous functions (or functions called later) and when we do not know the exact arguments

4. The new keyword

   new keyword when called will create a new object. The this refers to the new object.