this
keyword to refer to the instance of the class. E.g., consider this case:this
refers to an instance of the Toppings
class. As long as the list
method is called using dot notation, like myToppings.list()
, then this.formatToppings(this.toppings)
invokes the formatToppings()
method defined on the instance of the class. This will also ensure that inside formatToppings
, this
refers to the same instance.this
can also refer to other things. There are two basic cases that you should remember.this
used inside someMethod
will refer to someObject
, which is usually what you want.this
used inside someFunction
can refer to different things depending on whether we are in "strict" mode or not. Without using the "strict" mode, this
refers to the context in which someFunction()
was called. This is rarely what you want, and it can be confusing when this
is not what you were expecting, because of where the function was called from. In "strict" mode, this
would be undefined, which is slightly less confusing.log
expects this
to refer to console
, but the reference was lost when the function was detached from console
.this
explicitly. One way to do this is by using bind()
method, which allows you to specify the value to use for this
inside the bound function.Function.call
and Function.apply
, but we won't discuss this here.this
can be confusing is with respect to anonymous functions, or functions declared within other functions. Consider the following:this
will not point to the expected object: in "strict" mode it will be undefined
. This leads to another ES6 feature - arrow functions, which will be covered next.