Java script:About function within an object

Question

not sure whats the this used for: "this.changeName = changeName;" if i delete this line the code doesn't work fine. But this line seems do nothing.

<!DOCTYPE html>
<html>
<body>
<script>
function person(firstname,lastname,age,eyecolor)
{
this.firstname=firstname;
this.lastname=lastname;
this.age=age;
this.eyecolor=eyecolor;
this.changeName = changeName;
function changeName(name)
{
this.lastname=name;
}
}
myMother=new person("Sally","Rally",48,"green");
myMother.changeName("Doe");
document.write(myMother.changeName);
</script>

</body>
</html>

I think your confusion is a result of `variable hoisting`. You should see this thread for discussion on the topic: http://stackoverflow.com/questions/3725546/variable-hoisting — megawac, Nov 20 '13 at 18:17
Hi! My answer solve your problem? If so check as "correct", if not tell me what is missing. — Protomen, Apr 12 '15 at 15:22

score 1 · Answer 1 · answered Nov 20 '13 at 18:14

1

this.changename assigns the private changeName function to the Objects instance. So, when you create a new Object of type person, person has the method changename because of this.changename which assigns changeName as the function to execute.

answered Nov 20 '13 at 18:14

tymeJV

103,943
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It doesn't assign it to the prototype, assigns it to the instance – megawac Nov 20 '13 at 18:14

score 0 · Answer 2 · answered Nov 20 '13 at 18:15

0

Try:

function person(firstname,lastname,age,eyecolor)
{
this.firstname=firstname;
this.lastname=lastname;
this.age=age;
this.eyecolor=eyecolor;
this.changeName = function(name) {
this.lastname=name;
}
}

answered Nov 20 '13 at 18:15

Protomen

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score 0 · Answer 3 · answered Nov 20 '13 at 18:16

0

You can also use :

this.changeName = function(name)
{
this.lastname=name;
}

answered Nov 20 '13 at 18:16

Ankit Tyagi

2,381
10
19

score 0 · Answer 4 · answered Nov 20 '13 at 18:26

The function changeName is a method on the object person, which you set when you say this.changeName = changeName; this meaning the person object.

You're not using that function until you call it here myMother.changeName("Doe");

In which you are changing the last name to "Doe" So myMother.lastname = "Doe"

I'm kind of repeating what the others are saying, but hoping that it is more clear.

Java script:About function within an object

4 Answers4