Question about methods.

Hi!

I am pretty new to Javascript and I've read a few pages about Objects and Methods, but I think I'm still fuzzy on a few things I hope someone can clear things up!

Code:

---

function pizza()
{
  this.cooked = false;
  var spoiled = false;
 
  this.cook = cook;
  function cook(){
    cooked = true;
  }
  function spoil(){
    spoiled = true;
  }
}

---

Is spoil() private and cook() public?
If so then are the variables treated the same?

I am coming from a C++ background just trying to translate things over to where I'm comfortable. I'm so used to using classes I feel weird trying to program without them.

Any additional information pertaining to methods and objects that I didn't directly ask for is more than welcome.

Thank you for your time,
Happy Holidays.

Well it seems if I don't make a function preceed with the declaration and definition

Code:

---

this.functionName = functionName;
function functionName(){
}

---

Then I can't call that function later which relates to my thoughts on public and private. On the other hand it seems if a variable inside a function isn't given a

Code:

---

this.variableName = something;

---

but rather

Code:

---

variableName = something;

---

Then all the objects of the same type will share the same value of variableName....
does

Code:

---

this.variableName

---

make it unique or am I just using variables out of scope and dealing with undefined behavior as results?

I'll try to explain...

Quote:

---

Originally Posted by Lesshardtoofind

Code:

---

function pizza()
{
  this.cooked = false;
  var spoiled = false;


  this.cook = cook;
  function cook(){
    cooked = true;
  }
  function spoil(){
    spoiled = true;
  }
}

---

---

'this' is a reference to the new object you've created and has no custom properties in the beginning of the pizza function. this.cooked = false adds a new (public) property cooked to the object. (All properties of all objects are actually public.) var spoiled = false creates a locally accessible variable spoiled inside the scope of the pizza function. It's not really a property of the object directly (because you don't say this.spoiled = false), but the variable is only accessible inside the pizza function (including inside functions and methods created inside the pizza function) so I suppose you could call spoiled private.

Like with the cooked property, this.cook = cook adds a new (public) property cook which will contain the local cook function. (It'll be a method in other words.) This does work in JavaScript because it doesn't matter whether you declare/define functions before or after you call or reference them:

Code:

---

function a() {
  alert('A');
}
a(); // works
b(); // also works
function b() {
  alert('B');
}

---

Your cook method could also be created like this:

Code:

---

this.cook = function() {
  cooked = true;
};

---

However, there is something that won't work as expected in your cook function: cooked = true will actually set a global variable cooked (because cooked has not been declared with var anywhere in the code, thus it's considered a global). It should say this.cooked = true because you want to set the (public) property of the object.

spoiled = true does as expected though - it sets the locally accessible variable spoiled inside the pizza function.

To sum it up: use this when dealing with public properties, and use var when declaring private properties. And to answer your question - yes, spoil() is private and cook is public (even though private and public might not be completely accurate words to use in JavaScript).

Thanks for the response. I was trying to get things sorted out as I wasn't getting the results I expected from methods I was using. I eventually got the game to behave, but I wanted to know WHY everything was working the way it was.