merge json object with arrays

Question

Suppose I have two json objects and I need to merge them.

css: [{
        drag: "mode() == 'layout'",
        ui_draggable: "mode() == 'layout'"
}]

css: [{
        someclass : true
}]

I want to end up with:

css: [{
        drag: "mode() == 'layout'",
        ui_draggable: "mode() == 'layout'",
        someclass : true
}]

After some further trial I came up with this but I assume I have place a few bugs or useless lines of code in it.

I came up with this code after a little playing around. My needs didn't need to recurse more than two levels so this is just fine. It could be much refined I am sure but it works great for binding knockout. Here is an example of how I used it to extend jquery unobtrusive knockoutjs

    var settings = {
        text: 'SelectedCard().CardData.Title',
        visible: "mode() != 'edit' || !isMyCard()",
        css: [{ drag: "mode() == 'layout'" , selectedElement: "selectedCardElement() == '_titlePreview'"}]
    };
    var settings2 = 
        {
            css: [{ drag: "mode() == 'layout'"}]
    };
   var settings3 =  merge(settings, settings2);

function merge(first, second) {

    for (var a1 in first) {
        // if second object is null we are finished.
        used.push(a1);
        if (second[a1] == null) {
            continue;
        } else {

            var ob2 = second[a1];
            if (typeof (first[a1]) != typeof (ob2)) {
            throw new Error("conflicting properties named:" + a1);
            }

            if ($.isArray(first[a1])) {

                for (var i = 0; i < ob2.length; i++) {
                    first[a1].push(ob2[i]);
                }

            } else {
                // matching property. 
                return merge(first[a1], second[a1]);
            }
        }
    }
    for (var a2 in second) {
        if (used.indexOf(a2) < 0) {
            first[a2] = second[a2];
        }
    }
    return first;
}

These are not "JSON objects". JSON is a string. These are objects. — Jonathan M
– Jonathan M, Commented May 21, 2012 at 20:45
google.com/search?q=javascript+objects+merge SO is not your Personal Research Assistant. — iambriansreed
– iambriansreed, Commented May 21, 2012 at 20:46

Dave Romero · Accepted Answer · 2012-05-21 22:29:37Z

3

1) To merge both objects with a one-way overwrite, this will do it:

for (var attrname in obj2) { 
    obj1[attrname] = obj2[attrname]; 
}

2) To merge selectively, both ways:

obj1.someclass = obj2.someclass;

-or-

obj2["someclass"] = obj1["someclass"];

In this case, if the property does not yet exist in the object it does not need to be defined before assigning it.

3) Consider using a library like Underscore.js for performing "array functions" similar to this:

_.union([1, 2, 3], [101, 2, 1, 10], [2, 1]);

returns [1, 2, 3, 101, 10]

4) Lastly, here's a strong resource for formatting JSON objects, arrays and a combination thereof: jsonexample.com. This will be helpful as you get into complex "array functions".

Cheers!

answered May 21, 2012 at 22:29

Dave Romero

1386 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

merge json object with arrays

1 Answer 1

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related