CODEWITHSUNDEEP
javascriptscope
Emanuele Coppola
Emanuele Coppola

Reputation: 304

How to access to "this" variable outside the object

I'm making a js canvas plugin, and I made this object:

function MyObject(argument) {
   var self = this;

   var callback = argument.callback;

   this.onRequestAnimationFrame = function() {
       callback(self);
   }

   this.myFunction = function (){
       return false;
   }
}

and I call it like this

var customObject = new MyObject({
    callback: function(instanceClass){
       instanceClass.myFunction();
    }
})

The problem is, I must get the instance class and call a function from it, but I get "myFunction is not a function" from the console.

Upvotes: 0

Views: 189

Answers (2)

ajayv
ajayv

Reputation: 703

When we make a constructor call, if we are not returning any object then function returns a 'this' object which is in its lexical scope.

when you write this,

var customObject = new MyObject({
    callback: function(instanceClass){
       instanceClass.myFunction();
    }
});

function MyObject returns its 'this' object.

So, we can call 'onRequestAnimationFrame' function which in return call the callback.

customObject.onRequestAnimationFrame();

jsbin link: http://jsbin.com/foxupakihi/edit?js,console

Upvotes: 0

speciesUnknown
speciesUnknown

Reputation: 1753

You don't access "this" from outside the object.

The way you have written this, you need to instance the object, at which point myFunction will be a method of the object.

"this" is not a variable, but a keyword.

function MyObject(argument) {
   var self = this;

   var callback = argument.callback;

   this.onRequestAnimationFrame = function() {
       callback(self);
   }

   this.myFunction = function (){
       return false;
   }
}

function callback (caller) {
    console.log(caller.myFunction());
};

var a = new MyObject({callback : callback});

Upvotes: 2

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