CODEWITHSUNDEEP
javascript
manraj82
manraj82

Reputation: 6305

Updating a part of the object works but it updates even before I update it

Im updating a part of an object and the update works fine.Its when I did a console.log on the object before the I called the update functio,n the object was already updated.I was expecting to see the old copy of the object,i know Im doing something really silly.I just want to understand why this is happening.Here is my code

function updateObject(o){
            o.a='oneHundred';
            o.b='twoHundred'
        }

        var obj={
            a : 'one',
            b : 'two',
            c : {
                    a : '',
                    b : ''
                }
        }

        console.log(obj);//outputs the updated object before I call updateObject()

        var upObject = obj.c ;

        updateObject(upObject);

        console.log(obj);

Upvotes: 1

Views: 130

Answers (2)

Dennis
Dennis

Reputation: 32598

Chrome will display the object itself in the console, not a representation of the object at that point in time. You can call stringify to get a snapshot and log that so it won't change when you change the object.

console.log(JSON.stringify(obj));

Upvotes: 2

JaredMcAteer
JaredMcAteer

Reputation: 22535

Chrome (and possibly firebug) doesn't actually log the current state of an object until you observe it. If you put a breakpoint in the code like so:

    console.log(obj);//outputs the updated object before I call updateObject()
    debugger; // force breakpoint
    var upObject = obj.c ;

    updateObject(upObject);

    console.log(obj);

and then expand the object you will see that it's the un-updated version. You're better off logging the specific properties you want to see rather than entire objects when you can.

Upvotes: 3

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