CODEWITHSUNDEEP
javascriptobject
Inigo
Inigo

Reputation: 8685

updating value within object using "this"

I am trying to update a value from within the object itself. I have the following code:

    var stepData = {
        0: {
            ref: "Home",
            values: {

            },
            init: function(){
                stepData[1].ref = 'new value';
                alert(stepData[1].ref);
                return;
            },
            save: function(){

            }
        },
        1: {
            ref: "one"
        }
     }

    $("#run").click(function(){
        stepData[0].init();
    });

Which works fine. However, I can't replace

stepData[1].ref = 'new value';
alert(stepData[1].ref);

with

this[1].ref = 'new value';
alert(this[1].ref);

Why not?

EDIT: sorry, mistake in original code. Fixed now.

Upvotes: 1

Views: 37

Answers (2)

JLRishe
JLRishe

Reputation: 101690

It doesn't work because if you call stepData[0].init(), then this refers to stepData[0], not stepData.

One way to improve the situation is to use an immediately invoked function to create your object:

var stepData = (function(){
    var mySelf = {
        0: {
            ref: "Home",
            values: {
            },
            init: function(){
                mySelf[1].ref = 'new value';
                alert(mySelf[1].ref);
                return;
            },
            save: function(){

            }
        },
        1: {
            ref: "one"
        }
    };

    return mySelf;
})();

The following will break the code that you have now:

var newVariable = stepData;
stepData = null;
newVariable[0].init();

but it will not break the approach above.

Upvotes: 0

T.J. Crowder
T.J. Crowder

Reputation: 1074385

this is set primarily by how a function is called, not where it's defined. Your code:

$("#run").click(function(){
    stepData[0].init();
});

...calls init with this set to stepData[0].

You can call it with this set to stepData if you like, using Function#call:

$("#run").click(function(){
    stepData[0].init.call(stepData);
});

From your comment on the question:

So the way I've got it is OK then?

Yes, as long as stepData is a singleton, there's no particular need to use this in its functions.

More about this (on my blog):

Upvotes: 1

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