Needs some clarification on JS objects please

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November 15th, 2012, 06:02 AM

mind_grapes

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Other - Needs some clarification on JS objects please

Hello All,

Again, not wishing to beat the "new to JS" drum, but i really am, and so, im after some clarification about objects, namely the ability to add methods to objects that have been created within a function (i think that's the right expression?)

Here is the example im working with - found over at w3s:

Code:

<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.lastname);
</script>

While I understand the ability to amend the last name here, the question i have is:

Q. can you modify the firstname within the same function - dont know how this would be done - or do you have to create a new function all together like this?

Code:

<script>
function person(firstname,lastname,age,eyecolor)
{
this.firstname=firstname;
this.lastname=lastname;
this.age=age;
this.eyecolor=eyecolor;
 
this.changeName=changeName;
this.changeFirst=changeFirst;

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

function changeFirst(fname)
{
this.firstname=fname
}
}

myMother=new person("Sally","Rally",48,"green");
myMother.changeName("Doe");
myMother.changeFirst(" blah blah");

document.write(myMother.lastname + myMother.firstname);
</script>

this was my attempt as i dont know how this would be achieved within the first code.

Apologies if this is trivial, and not what the forums are for.

Your help is most appreciate

Kind regards
MG

November 15th, 2012, 07:27 AM

Jacques1

pollyanna

Join Date: Jul 2012

Location: Germany

Posts: 1,864

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Hi,

first of all: Don't use w3schools for learning. It's known to be a bad resource that contains a lot of false information and bad advice (like using document.write()).

As to your question:

You can change and add object properties wherever and whenever you want. For example, you could directly change the firstname property on the top level outside of any function/method:

Code:

myMother.firstname = 'xyz';

And of course you can also change the firstname in the changeName() method:

Code:

function changeName(first, last)
{
	this.firstname = first;
	this.lastname = last;
}

Just try it out.

November 15th, 2012, 07:42 AM

mind_grapes

Contributing User

Join Date: Aug 2009

Posts: 153

Time spent in forums: 1 Day 13 h 5 m 54 sec
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Hi,

thanks for the reply, and the advice.

Can you recommend any other sites please? is tizag any good? i never know which one to use so i default to w3s.

ha, you're right:

Code:


function changeName(first, last)
{
this.firstname=first;
this.lastname=last;
}
}
myMother=new person("Sally","Rally",48,"green");
myMother.first="first "
myMother.last="last"
document.write(myMother.first + myMother.last);

Thanks once again.

Kind regards
MG

November 15th, 2012, 07:44 AM

Winters

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http://forums.devshed.com/showpost....036&postcount=8.

November 15th, 2012, 07:55 AM

mind_grapes

Contributing User

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Thank you.

W3Schools had me fooled. I thought they were a part of W3C ! ! Doh!

Regards
MG

November 15th, 2012, 08:26 AM

Jacques1

pollyanna

Join Date: Jul 2012

Location: Germany

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Quote:

Originally Posted by mind_grapes

W3Schools had me fooled. I thought they were a part of W3C ! ! Doh!

Yeah, that's probably what everyone thinks at first. And that's hardly a coincidence. They work hard to make it look like they're some "official" reference to sell their damn "certificates".

By the way, be careful with semicolons in your code. You forgot them in the two lines where you set the properties.

November 15th, 2012, 09:07 AM

mind_grapes

Contributing User

Join Date: Aug 2009

Posts: 153

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Hi,

Yeah, i keep forgetting certain characters. Ill try to remember in future.

Thanks.

Regards
MG

Other - Needs some clarification on JS objects please

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