JS object property undefined when called within object the first time

Question

Consider the following JS object, it has:

x: a variable given value 100
p: prints value of x, called immediately after creation
y: prints value of x, called after object creation

When the value of Pipe.x is printed immediately during Object creation, for some reason Pipe.x is undefined but when P.y() is called, after an object, the Object has been created, the Value of Pipe.x is 100, as it should have been in the first place.

var Pipe = {
    x: 100,

    p: function(){
        console.log('p says x is ' + this.x); // prints y says x is undefined
    }(),    // call immediately

    y: function(){
        console.log('y says x is ' + this.x);
    }
}

Pipe.y();    // prints y says x is 100

Is there any JS object property I'm missing which makes Pipe.p() print undefined and P.y() print 100?

mplungjan · Accepted Answer · 2018-04-08 07:53:49Z

5

The this Context depends on how it is being called. When you call Pipe.y(), it is equivalent to obj.method() and this will be pointed to obj, in this case Pipe.

When p is being executed as IIFE, this is set to window and there is no x on window

edited Apr 8, 2018 at 7:53

mplungjan

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answered Apr 8, 2018 at 6:53

sridhar..

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1 Comment

Suhail Gulzar Over a year ago

Oh, that does make sense. Also, considering the above condition, is there any way that I can get value of x within p, even when p() is executed as IIFE?

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