Prototype declared function is not a function

Question

var AnArray=(function(){
    var anArray=[];

    AnArray.prototype.getAnArray=function(){
        return anArray;
    }

    AnArray.prototype.setArray=function(id,val){
        anArray[id]=val;
    }
});

var objAnArray=new AnArray();

console.log(objAnArray.getAnArray());

When I try to call objAnArray.getAnArray(); it returns that it is not a function

However this below works fine

var Index=(function(){
    var Index=1;

    Index.prototype.getIndex=function(){
        return Index;
    }
    Index.prototype.setIndex=function(val){
        Index=val;
    }
});

var objIndex=new Index();

console.log(objIndex.getIndex());

Are prototypes unable to return arrays?

Answer 1

You're using anArray as an object, not an array. Use:

this.anArray = {}; // not []

---

Also your code looks weird. You declare the prototype in the constructor. Declare it like this instead:

function AnArray() {
    this.anArray = {};
}

AnArray.prototype.getArray=function(){
    return this.anArray;
}

AnArray.prototype.setArray=function(id,val){
    this.anArray[id]=val;
}

In your constructor you redeclare the prototype and bind the private variable anArray in every instance to the last instance of AnArray.

Same with Index.

This demonstrates the bad behaviour:

var AnArray=(function(){
    var anArray={};

    AnArray.prototype.getArray=function(){
        return anArray;
    }

    AnArray.prototype.setArray=function(id,val){
        anArray[id]=val;
    }
});
var a = new AnArray();
var b = new AnArray();
a.setArray("foo", "bar");
b.getArray(); // { foo: "bar" }