Get object with differing values

Question

I want to generate an object from two given objects A and B with only the values from B that differ from A. We can assume that the all fields exist in both A and B.

Example: Given the following two objects:

A

{
    "firstName": "John",
    "lastName": "Doe",
    "nickname": "Johnny",
    "location": {
        "latitude": 1.0,
        "longitude": 1.0
    },
    "email": "[email protected]"
}

B

{
    "firstName": "John",
    "lastName": "Doe",
    "nickname": "John-Boy",
    "location": {
        "latitude": 1.0,
        "longitude": 2.0
    },
    "email": "[email protected]"
}

As nickname and location have changed, I want the result to be:

{
    "nickname": "John-Boy",
    "location": {
        "latitude": 1.0,
        "longitude": 2.0
    }
}

Note that I want the full location object and not just the changed longitude

What would be a good way of achieving this?

See: How can I get a list of the differences between two JavaScript object graphs? and Generic deep diff between two objects. Please search the site before posting. — Mr. Polywhirl
– Mr. Polywhirl, Commented Jan 12, 2015 at 11:29
1. I did. For about 15 minutes. 2. Please read my question before drawing conclusions. I don't want a diff. I want a subset of B. Essentially B minus the common values of A and B. Maybe I need to clarify it further? — Gustav Karlsson
– Gustav Karlsson, Commented Jan 12, 2015 at 12:09

Yonatan Ayalon · Accepted Answer · 2015-01-12 14:51:33Z

var array1 = {
    "firstName": "John",
    "lastName": "Doe",
    "nickname": "Johnny",
    "location": {
        "latitude": 1.0,
        "longitude": 1.0
    },
    "email": "[email protected]"
}

var array2 = {
    "firstName": "John",
    "lastName": "Doe",
    "nickname": "John-Boy",
    "location": {
        "latitude": 1.0,
        "longitude": 2.0
    },
    "email": "[email protected]"
}

var currentString;
		var resultObject = {};
	function loopOverObject(sourceObj, targetObj,innerObjName) {
		for (var key in sourceObj) {
			currentString = null;
			if (sourceObj.hasOwnProperty(key)) {
				
				if (typeof sourceObj[key] === "object") {
					loopOverObject(sourceObj[key],targetObj,key);
					break;
				}
				else {
					if (sourceObj[key] !== targetObj[key]) {
						if (innerObjName) {
							if (resultObject[innerObjName]) {
								resultObject[innerObjName][key] = sourceObj[key];
							}
							else {
								resultObject[innerObjName] = JSON.parse('{"'+key+'": '+sourceObj[key]+'}');
							}
						}
						else {
							currentString = sourceObj[key];
						}
					}
				}
				if (currentString) {
					resultObject[key]=currentString;
				}
			}
		}
		return resultObject;
	};
	var result = loopOverObject(array2,array1);
	
var resultDiv = document.getElementById("result")
resultDiv.innerHTML = JSON.stringify(result);

<div id="result"></div>

B T · Accepted Answer · 2015-07-06 20:36:02Z

0

You could use a differencing module like odiff by getting the list of differences and using them to build a new object appropriately:

var diff = odiff(A,B)
var result= {}
for(var n=0; n<diff.length; n++) {
  var key = diff.path[0] // the top-level key
  result[key] = B[key]
}

Then you got the result I think you want - that is if you only care about getting the top-level fields that have changed.

answered Jul 6, 2015 at 20:36

B T

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