javascript-this

Question 1

What is this in JavaScript?

Answer 1

this is an implicit parameter that accesses the object that contains that this keyword when that property or method is called.

Question 2

What does it mean to say that this is an “implicit parameter”?

Answer 2

An implicit parameter is a parameter that does not have to be explicitly added during the function definition.

Question 3

When is the value of this determined in a function; call time or definition time?

Answer 3

During call time.

Question 4

How can you tell what the value of this will be for a particular function or method definition?

Answer 4

You cannot tell what this will equal until it is called.

Question 5

How can you tell what the value of this is for a particular function or method call?

Answer 5

Check the object containing the method when it is called and that will have the value of this or for a function with no containing object it will have the global Window object as its “this” object. If there is an object name to the left of a method call then the this value will be that object.