javascript-this

Question 1

What is this in JavaScript?

Answer 1

implicit paramater in a js function

Question 2

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

Answer 2

its there even though you don’t actually see it, its implied even though you can’t see it

Question 3

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

Answer 3

the call time

in a definition, this has no value

Question 4

What does this refer to in the following code snippet?

var character = {
firstName: ‘Mario’,
greet: function () {
var message = ‘It's-a-me, ‘ + this.firstName + ‘!’;
console.log(message);
}
};

Answer 4

character

Question 5

Given the above character object, what is the result of the following code snippet? Why?
character.greet();

Answer 5

the result is “it’s a me Mario”
greet is being called off of character so this will be character

Question 6

Given the above character object, what is the result of the following code snippet? Why?
var hello = character.greet;
hello();

Answer 6

hello its a me, undefined

Question 7

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

Answer 7

you look to the left of the dot. in order to do this the function must be in the process of being called. if it is not being called and is only defined then the valure of this will be window. but that doesn’t matter, the point is that in this situation you have no control over the value of this which you need to have