CODEWITHSUNDEEP
javascriptclassoop
GoldenerAal
GoldenerAal

Reputation: 91

JavaScript Class Best Practice?

I'm currently looking into different patterns for building classes in JavaScript. But no matther what pattern I see, there are still some things I am not really sure about. 

var ItemManager = (function()
{
    var p = function()
    {
        this.items= [];
    };

    p.prototype.addItem = function(item)
    {
        var self = this;    
        self.items.push(item);
    };

    return p;
}());

I create the simple class ItemManager, this class got the function addItem for adding any item to the collection. Now I don't really want the variable items, which represents the collection, to be public, this variable should be private, but I don't see any possible way to use a prototyped method to access private variables.

So what's the best practice in this case? Simply don't use private variables?

Upvotes: 6

Views: 5542

Answers (3)

Peter Tseng
Peter Tseng

Reputation: 13993

There are several ways to have private variables:

I favor Symbols, though they can still be found using reflection (i.e. not completely private). Example:

var Person = (function() {
    var nameSymbol = Symbol('name');
​
    function Person(name) {
        this[nameSymbol] = name;
    }
​
    Person.prototype.getName = function() {
        return this[nameSymbol];
    };
​
    return Person;
}());

So it's possible to have (reasonably) private variables, but unfortunately none of the solutions are as elegant as you'd like.

Upvotes: 1

aga
aga

Reputation: 29416

var ItemManager = function() {
    var items = [];

    return {
           addItem : function(item) {   
               items.push(item);
           },
           removeItem : function() {
                return items.pop();
           }
     }
};

var myItemManager = new ItemManager();

items variable becomes hidden after the execution of ItemManager function, but addItem and removeItem still share the access to items. See the Douglas Crockford's article on private variables in JavaScript for further investigation.

Upvotes: 6

tommy knocker
tommy knocker

Reputation: 371

as GoldenerAal mentioned, they are not called classes, but functions you have 

var ItemManager = function (){
..
...
...

};

you could have:

function ItemManager(){
this.items = [];

function addItem(item){
...
};
};

you can then create an instance of ItemManager, only when you need to :

var itemManager = new ItemManager();
itemManager.addItem(<something here>);

http://javascript.crockford.com/private.html variables inside a function only have the scope of that function, that variable is not a global variable (static variable).

Upvotes: -1

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