This with prototype in javascript

Question

Am just a beginner in JavaScript and I found this keyword really difficult to understand for me. I know this depends on how the function is invoked.

The code is .

MyClass = function() {
    this.element = $('#element');

    this.myValue = 'something';

    // some more code
}

MyClass.prototype.myfunc = function() {
    this.element.click(function() {

    });
}

new MyClass();

I just need to know what this denotes in this.element.click(function() {}

Does it denote Myclass? Please help me in understanding the use of this keyword in prototype functions in JavaScript.

Myclass is a constructor. When you create a new object from it using new, this refers to that new object. — Andy
– Andy, Commented Apr 11, 2014 at 9:34
Brother there are no more links to refer am not geting its informarion properly..:( — user3517846
– user3517846, Commented Apr 11, 2014 at 9:34
You can check the right side(Related column) of this particular question. stackoverflow.com/questions/310870/… — Roy M J
– Roy M J, Commented Apr 11, 2014 at 9:35
Using a debugger, setting a break point and examining the value will give empiric insight. For the theory read a good book on JavaScript. — mvw
– mvw, Commented Apr 11, 2014 at 9:36

T.J. Crowder · Accepted Answer · 2014-04-11 09:33:39Z

2

I just need to know what this denotes in this.element.click(function() {}

Most likely, it's the object created by a new MyClass() expression. When you do new MyClass(), the JavaScript engine creates a new object, assigns MyClass.prototype as the object's underlying prototype, and then calls MyClass with this pointing to the new object. It returns that object as the result of the expression:

var o = new MyClass();

At this point, if you do:

o.myfunc();

...then within myfunc, this will be equal to o.

this is a slippery concept in JavaScript, though, which is why I said "most likely" above. More (on my blog):

answered Apr 11, 2014 at 9:33

T.J. Crowder

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3 Comments

user3517846 Over a year ago

so if i call var b = Myclass()..Then this keyword in the function will be b ..right ?

T.J. Crowder Over a year ago

@user3517846: No, you need the new in there: var b = new MyClass(); Then, this will be b within the call, provided you call myfunc like this: b.myfunc();

user3517846 Over a year ago

Got it and thanks ..:D ..:D ..and this is applicable only in the case of prototypes right ?

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