Why is the jQuery extend method not copying my javascript object?

Question

I've looked into the many posts here regarding cloning and copying javascript objects, notably, these two topics:

It seems like it's not working for me, though.

Here is a snippet of code I'm using:

var copiedObject = {};

$.getJSON(URL, null, function (data) {
     copiedObject = jQuery.extend(true, {}, data);
});

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

If I have my console log function within the JSON call, it outputs the proper values, but after the function, it's emptied out, and outputs {}.

I've tried using copiedObject = JSON.parse(JSON.stringify(data)), as well as the clone(obj) function from the "Copying an object in Javascript" post, all to no avail.

Am I missing something?

Did you try console.log(copiedObject); (without the JSON.stringify)? — JoeFletch
– JoeFletch, Commented Oct 26, 2012 at 15:39

jAndy · Accepted Answer · 2012-10-26 15:40:12Z

8

$.getJSON fires an Ajax request, which by default runs asyncronous. Your console.log will fire before the request has finished. Fix it by moving the console output into the callback.

$.getJSON(URL, null, function (data) {
     copiedObject = jQuery.extend(true, {}, data);
     console.log(JSON.stringify(copiedObject));
});

answered Oct 26, 2012 at 15:40

jAndy

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2 Comments

D'Arcy Rail-Ip Over a year ago

Thank you, but will my object retain it's values outside of that function? I'm trying to limit the number of times I have to make this ajax request.

jAndy Over a year ago

@Rail24: yes. If copiedObject is contained by a higher parent scope, you can access its value in any child-scope. All you need to make sure is, that every piece of code which accesses that variable executes after the request has finished.

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