Copying AJAX JSON object into existing Object

14
votes

I have several Javascript prototypes. Initially, instances will have only ID's filled in, with some generic place holder information for other data. I then send a message to the server with the ID and the object type (using jQuery's AJAX function) and the server returns a JSON object with all the missing information (but no ID). The variables in the returned object have the exact same name as those in the existing object.

What's the easiest way to transfer this into the existing empty object? I've come up with a few alternatives

  • set the object equal to the returned object, then copy in the id (loses prototype functions?)
  • create a function for each object that takes an object with identical structure and copies the data
  • loop through the key-value pairs of the JSON object to and copy them to existing object

If I use the third option, is this the correct way to do that? :

for (var key in json) {
    if (object.hasOwnProperty(key)) {
        object[key] = json[key];
    }
}

assuming json is the returned object and object is the existing object.

3
javascriptjqueryajaxjson
If json is plain JSON then I don't think you even need the hasOwnProperty check. Unless someone has been funking with Object.prototype. – Paul Grime
The question is, what do you want to do with your JSON-Object. If you want to evaluate to an object, JSON.parse() does the trick for you. If you want to merge it to an existing object, jQuery.extend() would be a better suggestion. – Thomas Junk
@PaulGrime I'm doing that as a precaution in case there's an extra key in the json object that I don't want in the existing object. If you'll notice, I'm looping through keys in json but checking against object. – Jaws212

3 Answers

13
votes

Try this using extend():

var newObject = jQuery.extend({}, oldObject);
8
votes

Alternative without jQuery is to use the javascript Object.assign method.

Object.assign(targetObject, json);

1
votes

You can use jQuery.extend: http://api.jquery.com/jQuery.extend/

$.extend(object1,object2);

If your JSON is a string then create an object from that first:

var object1=$.parseJSON(myJsonString);