Merge JavaScript objects

Question

I've read another similiar question on SO but there wasn't a clear answer at that question.

I got some JavaScript objects that look like this:

var moveJSON = {
    'name'      : move[0].innerHTML,
    'info'      : move[1].innerHTML,
    'power'     : move[2].innerHTML,
    'accuracy'  : move[3].innerHTML,
    'type'      : move[4].innerHTML,
    'category'  : move[5].innerHTML,
    'pp_min'    : move[6].innerHTML,
    'pp_max'    : move[7].innerHTML
}

I need to merge them into one object, that will be send to PHP via AJAX. But first: what's the best way to merge them into a single object (array)?

Is this question similar to: stackoverflow.com/questions/1198962/… ? — Nathan Feger
– Nathan Feger, Commented Nov 16, 2009 at 22:34

Justin Johnson · Accepted Answer · 2010-06-27 19:42:18Z

"Merging" objects is different than putting objects into an array, which is an aggregation. Although it provides you with a single object to pass around, this aggregate is structurally different than a merged object. Aggregating adds a level of depth when accessing values in the new container, which is an array. This is different from merging which results in the same container, an object.

If you're using Dojo, than you can just do:

var mergedObject = dojo.mixin(object1, object2);

Otherwise, here's a simple way of merging two or more objects:

var merge = function() {
    var result = {},
        length = arguments.length,
        object = null,
        key    = null;

    if ( length < 2 ) {
        throw "Must merge two or more objects";
    }

    for ( var i=0; i<length; ++i ) {
        object = arguments[i];
        for ( var key in object ) {
            if ( !object.hasOwnProperty(key) ) { continue; }
            result[key] = object[key];
        }
    }
    return result;
};

var mergedObject = merge({a:1}, {b:2, c:3, d: {a: 1}}, {a: 2, c:[1,2,3]});
// mergedObject looks like {a:4, b:2, c:[1,2,3], d:{a:1}}

As you'll see, this is very different than an aggregation:

var aggregate = function() {
    if ( length < 2 ) {
        throw "Must aggregate two or more objects";
    }

    // The following can be simplified to 
    //   return Array.prototype.slice.call(arguments);
    // but is left in a more explicit manner to illustrate the difference

    var result = [],
        length = arguments.length;

    for ( var i=0; i<length; ++i ) {
        if ( arguments.hasOwnProperty(i) ) {
            result.push(arguments[i]);
        }
    }

    return result;
};

var aggregation = aggregate({a:1}, {b:2, c:3, d: {a: 1}}, {a: 4, c:[1,2,3]});
// aggregation looks like [{a:1}, {b:2, c:3, d: {a: 1}}, {a: 4, c:[1,2,3]}];

So the difference is that mergedObject looks like {a:4, b:2, c:[1,2,3], d:{a:1}}, where property d is accessed as mergedObject.d, as opposed to aggregation, which looks like [{a:1}, {b:2, c:3, d: {a: 1}}, {a: 4, c:[1,2,3]}] and where property d is accessed as aggregation[1].d.

It should also be noted that an explicit function for aggregation isn't necessary thanks to the literal array definition syntax available in JavaScript

var aggregation = aggregate({a:1}, {b:2, c:3, d: {a: 1}}, {a: 4, c:[1,2,3]});

is equivalent to

var aggregation = [{a:1}, {b:2, c:3, d: {a: 1}}, {a: 4, c:[1,2,3]}];

kemiller2002 · Accepted Answer · 2009-11-17 13:01:06Z

4

This should work.

var array = []

array.push(yourObject);

this will put your object into an array, which should be used if you were putting of a collection of the same object into one.

to merge different values into one object:

function makeObject(){
        var obj = {};

 obj['info']  = somevalue;    //arguments [0] maybe
 obj['power']  = somevalue;    
 obj['accuracy']   = somevalue;
 obj['type']       = somevalue;
 obj['category']   = somevalue;
 obj['pp_min']     = somevalue;
 obj['pp_max']    = somevalue;

return obj;

}

Here is a link also describing passing arguments like array into a function in JavaScript which could be useful in creating the merged object.

http://www.cherny.com/webdev/60/javascript-function-arguments-default-values-passing-objects-and-overloading

edited Nov 17, 2009 at 13:01

answered Nov 16, 2009 at 21:26

kemiller2002

116k28 gold badges201 silver badges255 bronze badges

4 Comments

Justin Johnson Over a year ago

This is a collection or aggregation of objects, not a merge.

kemiller2002 Over a year ago

He mentions an array at the end of the post.

kemiller2002 Over a year ago

oh I see what he is saying now.

Justin Johnson Over a year ago

This is still nothing close to a merge.

Wessel Rossing · Accepted Answer · 2009-11-16 21:42:00Z

0

If you have multiple JSON objects, you can create a containing JSON object:

var containerJSON = {};

And use that object as an array:

containerJSON[0] = moveJSON_1;
containerJSON[1] = moveJSON_2;

Then in PHP you can use json_decode() to get your data back.

answered Nov 16, 2009 at 21:42

Wessel Rossing

931 silver badge10 bronze badges

2 Comments

Josh Stodola Over a year ago

Arrays are more appropriate in this case.

Wessel Rossing Over a year ago

When you send the data as an array to php, you will need to decode every JSON object individually. Therefor it is best to put them into an JSON "container" object.

jgchristopher · Accepted Answer · 2009-11-16 22:46:37Z

-1

This is a simple mixin function that will not overwrite existing object properties

var mixin = function(addToJSON, someOtherJSON) {
  for(var key in someOtherJSON) {
     // don't overwrite 
     if(!moveJSON[key]) {
       moveJSON[key] = someOtherJSON[key]; 
     }
  }
};

var otherJSON = {'someOtherStuff': someOtherMoves[0].innerHTML};

mixin(moveJSON, otherJSON);

That should do what you need.

answered Nov 16, 2009 at 22:46

jgchristopher

213 bronze badges

2 Comments

Justin Johnson Over a year ago

You should check your function, addToJSON is unused.

Justin Johnson Over a year ago

Also, values may be overwritten if they evaluate to false or 0. Instead you should use if ( typeof moveJSON[key] != "undefined" ) {

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