Computer Science Canada

Javascript TYS
Author:  wtd [ Mon Apr 30, 2007 1:00 am ]
Post subject:  Javascript TYS
Write a class Foo with private method bar that returns a string "bar". It should also have a public method baz that returns the result of bar, plus a string it takes as its solitary argument.
Author:  richcash [ Mon Apr 30, 2007 3:52 pm ]
Post subject:  Re: Javascript TYS
Is it like this?

answer? wrote:
<html>
<body>
<script type="text/javascript">

function Foo() {
bar = function() {
return "bar"
}
this.baz = function(str) {
return bar() + str
}
}
//object example
something = new Foo()
document.write(something.baz("s"))

</script>
</body>
</html>
Author:  wtd [ Mon Apr 30, 2007 9:02 pm ]
Post subject:  RE:Javascript TYS
Close, but you're missing one keyword, and the HTML was unnecessary.
Author:  wtd [ Mon Apr 30, 2007 9:17 pm ]
Post subject:  RE:Javascript TYS
For bonus points, explain the concept that permits a "private" method to be created in the manner you did.
Author:  richcash [ Mon Apr 30, 2007 10:22 pm ]
Post subject:  Re: Javascript TYS
I missed the "var' keyword, it should be before bar.

What I did was I created a global variable bar(). So when you go :
code:
objectOfFoo.bar()

it doesn't work, and it seems as if though bar() is private. But it's not, it's just that it doesn't belong to Foo or any of Foo's objects, it is global. Which means
code:
document.write(bar())
will actually work outside of the Foo class.
Author:  wtd [ Mon Apr 30, 2007 11:04 pm ]
Post subject:  RE:Javascript TYS
Yes, that's scoping.

Now, explain why "bar" is private in the following.

code:
function Foo() {
   var bar = function() {
      return "bar"
   }

   this.baz = function(str) {
      return bar() + str
   }
}
Author:  md [ Tue May 01, 2007 11:52 am ]
Post subject:  RE:Javascript TYS
Scope would make bar local to Foo, and thus "private".

:


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