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up vote 4 down vote favorite
1

I simulated a class in java script, It's code is here: 

function myclass()
{
    this.count ;

    this.init = function(){
        $("div.mybtn").click({n:this},function(e){
            e.data.n.count++;
        });
    }

    this.getCount = function(){
        alert(this.count);
    }
}

Then I created an instance of this class and executed it's method init(),But when I click on any div.mybtn element, It did not increment the value of this.count.
It seems the object this was passed to event handler by value not by reference.
How I can pass a variable to an event handler by reference?

Thanks for any help

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4 Answers

up vote 0 down vote accepted

Javascript doesn't have pass-by-reference parameters. For what you want, you should use a closure variable:

this.init = function(){
    var self = this;
    $("div.mybtn").click(function(){
        self.count++;
    });
}
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Perfect answer, write less do more !!! ,thanks – ABFORCE yesterday
up vote 3 down vote

You can't increment undefined, you have to start somewhere:

function myclass() {
    this.count=0;   // start counting at zero !!!

    this.init = function(){
        $("div.mybtn").on('click', {n:this},function(e){
            e.data.n.count++;
            e.data.n.getCount();
        });
    }

    this.getCount = function(){
        console.log(this.count);
    }
}

var c = new myclass();

c.init()

DEMONSTRATION

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I tested,Not worked! – ABFORCE yesterday
I tested as well, and works just fine. – adeneo 23 hours ago
up vote 0 down vote

You can write a bind function and bind the context with the event handler.

Function.prototype.bind = function(){
    var fn = this, args = Array.prototype.slice.call(arguments), object = args.shift();

    return function(){
        fn.apply(object, args.concat(Array.prototype.slice.call(arguments)));
    }
}

function myclass()
{
    this.count ;

    this.clicked = function(){
        this.count++;    
    };

    this.init = function(){
        $("div.mybtn").click(this.clicked.bind(this));
    }

    this.getCount = function(){
        alert(this.count);
    }
}
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Worked perfectly, But This is a bit complex :) – ABFORCE yesterday
up vote -1 down vote

There is no "pass by reference" available in JavaScript. You can pass an object (which is to say, you can pass-by-value a reference to an object) and then have a function modify the object contents:

       function alterObject(obj) {
          obj.foo = "hello world";
        }

        var myObj = { foo: "goodbye" };

        alterObject(myObj);

        alert(myObj.foo); // "hello world" instead of "goodbye"

REF HERE

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-1 This is not what I looking for – ABFORCE yesterday

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