javascript object literal - object creation

Question

I'm trying to create an object in which some properties rely on other previously defined properties, while trying to rely on object literals. Otherwise put, I'm trying to accomplish something like the following code (which is incorrect):

var mesh = {
            offset   : $('#mesh').offset(),
            position : $('#mesh').position(),
            height   : win.height - this.offset.top - 12,   
            width    : win.width - this.offset.left - 12,   
            limits   : {}
        }

as opposed to something of this sort (which works):

var mesh = {};
        mesh.offset   = $('#mesh').offset();
        mesh.position = $('#mesh').position();
        mesh.height   = win.height - mesh.offset.top - 12;  
        mesh.width    = win.width - mesh.offset.left - 12;
        mesh.limits = {};

So my question is rather simple: what is actually wrong with the first block of code and how can I correct it in order to create those new properties based on previously defined ones?

Ned Batchelder · Accepted Answer · 2012-04-28 13:57:59Z

3

There is no name that references the currently-building object literal. You'll need to use the second form, or have the values in variables that you can reference:

var offset = $('#mesh').offset();
var mesh = {
    offset   : offset,
    position : $('#mesh').position(),
    height   : win.height - offset.top - 12,   
    width    : win.width - offset.left - 12,   
    limits   : {}
}

answered Apr 28, 2012 at 13:57

Ned Batchelder

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6 Comments

Andrei Oniga Over a year ago

And there's no other way of accomplishing what I need?

Felix Kling Over a year ago

There a few ways. Have a look at stackoverflow.com/…

ddaa Over a year ago

There's no way of accomplishing what you ASKED, which is using object literal notation AND reusing previously defined attributes in the current object definition. There are many ways to achieve something that is functionally equivalent, and you provided one such way yourself.

ddaa Over a year ago

BTW, Ned, would you please wait a few minutes before giving perfect answers, so the rest of us get a chance ;-)

Andrei Oniga Over a year ago

@Felix Kling Thanks Felix. Those are actually the closest solutions to what I needed. Yet it seems that what I'm trying to accomplish is in fact, impossible.

|

Thomas Jones · Accepted Answer · 2012-04-28 14:04:26Z

0

you can create a constructor function

var Mesh = function(mesh_id){
    var mesh = $(mesh_id);
    this.offset = mesh.offset();
    this.position = mesh.position();
    this.height = win.height - this.offset.top - 12;
    this.width = win.width - offset.left - 12
    this.limits = {}


};

and then use it like this

var myMesh = new Mesh('#mesh')

*note that this code is assuming some variable win is defined. you have probably defined it as var win = $(window)

answered Apr 28, 2012 at 14:04

Thomas Jones

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3 Comments

ddaa Over a year ago

This is not answering the question, which is a about achieving this result using object literal notation.

Andrei Oniga Over a year ago

Indeed, this has nothing to do with taking advantage of the literal notation. I am in fact trying to avoid using constructors.

Thomas Jones Over a year ago

thats true ddaa. However, as you stated in your other comment, there is no way to do what he asked while sticking with an object literal. This is another alternative, though not exactly functionally equivalent, as I believe the memory gets allocated differently with constructor functions.

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