CODEWITHSUNDEEP
javascriptmodulescope
Jack
Jack

Reputation: 2285

Maintaining scope of 'this' within a constructor module

I'm trying to learn the module design pattern and I'm having trouble with scope in a nested method function. Other questions on the topic appear more advanced than what I'm doing. So, in the following code:

var myModule = function(){
  var myObject = {
    myArray: [],    //array of items
    addItem: function(arg){
            var item = {
                type: "example",
                value: arg
                }
            this.myArray.push(item);
        }
    }
  return myObject;
}

The method "addItem" doesn't seem to be adding the object to "myObject.myArray", but rather adding it to itself? Not quite sure. Can anyone give me a hint? Thanks in advance!

Upvotes: 0

Views: 42

Answers (3)

Tim P.
Tim P.

Reputation: 421

Stop trying to cheat death. just use prototype.

Something like:

var MyModule = function() {

    this.myArray = [];
};
MyModule.prototype.addItem = function(arg) {
    var item = {
        type : "example",
        value : arg
    };
    this.myArray.push(item);
};

And you would call it like:

var myModule = new MyModule()

myModule.addItem({
    better : 'way'
});

Upvotes: 1

milagvoniduak
milagvoniduak

Reputation: 3254

This will work as you expect and item will be pushed to the array of the myObject.

var myModule = function(){
var myObject = {
    myArray: [],    //array of items
    addItem: function(arg){
            var item = {
                type: value,
                value: arg
                }
            myObject.myArray.push(item);
        }
    }
    return myObject;
}

Though your 'value' var is not defined in the addItem function.

Upvotes: 1

VtoCorleone
VtoCorleone

Reputation: 17203

'this' is scoped to the addItem() function. You'd need to use

myObject.myArray.push(item);

You'll see a common practice where functions will set 'this' to another variable to reference later on inside of child functions/objects. 

var self = this;

or

var $this = this;

Upvotes: 1

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