How can I create a javascript class and access an internal collection using and index/name lookup?

I currently have this:

function SystemCollection () {
    this.systems = [];

    this.getSystem = function (id) {
        for(var s in this.systems) {
            if(s.num == id)
                return s;
        };

        return null;
    };

    this.add = function (system) {
        this.systems.push(system);
    };

    this.count = systems.length;
};

In C#, I'd do something like this:

class SystemCollection {

  private List<System> _foo = new List<System>();

  public System this[int index]
  {
    get { _foo[index]; }
  }

  public System this[string name]
  {
    get { return _foo.Where( x => x.Name == name).SingleOrDe开发者_StackOverflow中文版fault(); }
  }
}

I don't think you can override the this[] operator in javascript. But what you could do is this. I am assuming system has a property called name

this.add = function(system){
     this[system.name] = system;
}

then you can use the collection like this

collection[systemName];

Should do the trick, I hope. If this is not sufficient, then you can augment the value stored under the system name by wrapping it in an object or something like that.

Seems that you are trying to do a sort of key/value pair (systemId / systemName) collection.

The systems array should be private, handled internally only by the add and get methods.

Also since it is an array, you shouldn't use the for...in statement, a normal for loop it's enough, I think something like this:

API tests:

var test = new SystemCollection();
test.add(1, "System One");
test.add(2, "System Two");

test.count(); // 2
test.getSystemByName("System Two"); // Object id=2 name=System Two
test.getSystemById(1); // Object id=1 name=System One

Implementation:

function SystemCollection () {
  var systems = []; // private array

  // generic function to search by a property name
  function getSystem (value, propName) {
    var i, s;
      for(i = 0; i < systems.length; i++) {
        s = systems[i];
         if(s[propName] == value) {
            return s;
         }
      }
      // will return undefined if this point is reached
   }

   this.getSystemByName = function (name) {
     return getSystem(name, "name");
   };

   this.getSystemById = function (id) {
     return getSystem(id, "id");
   };

   this.add = function (systemId, systemName) {
     systems.push({id: systemId, name: systemName});
   };

   this.count = function () {
     return systems.length;
   };
}

I get the feeling that this C# like list will suit your purposes.

Code

function List() {

    this.count = 0;

    this.add = function(item) {
        this[this.count] = item;
        this.count++;
    }

    this.remove = function(index) {
        delete this[index];
        this.count--;
    }

}

Example

var list = new List();
list.add(1);
alert(list.count);
list.add(2);
alert(list.count);
alert(list[1]);