Difference in JSON objects using Javascript/JQuery

Question

I have two JSON objects in Javascript, identical except for the numerical values. It looks like this:

var data = {
  "eth0":{"Tx":"4136675","Rx":"13232319"},
  "eth1":{"Tx":"4","Rx":"0"},
  "lo":{"Tx":"471290","Rx":"471290"}
}

var old = {
  "eth0":{"Tx":"4136575","Rx":"13232219"},
  "eth1":{"Tx":"4","Rx":"0"},
  "lo":{"Tx":"471290","Rx":"471290"}
}

One object called "data" has the current values, another object called "old" has the same values from 1 second ago. I'd like to output a JSON object with only the change in values so I can calculate data throughput on the network interfaces.

var throughput = {
  "eth0":{"Tx":"100","Rx":"100"},
  "eth1":{"Tx":"0","Rx":"0"},
  "lo":{"Tx":"0","Rx":"0"}
}

I'm not sure how to go about traversing the JSON data - it could be for any number of interfaces.

Can anyone please lend me a hand? Thanks in advance

Answer 1

You can iterate through the parent and child object properties:

var diff = {};
for(var p in data){
  if (old.hasOwnProperty(p) && typeof(data[p]) == 'object'){
    diff[p] = {};
    for(var i in data[p]){
      if (old[p].hasOwnProperty(i)){
        diff[p][i] = data[p][i] - old[p][i];
      }
    }
  }
}

Answer 2

The basic premise for iterating over objects in JavaScript is like so

var whatever = {}; // object to iterate over
for ( var i in whatever )
{
  if ( whatever.hasOwnProperty( i ) )
  {
     // i is the property/key name
     // whatever[i] is the value at that property
  }
}

Fixing up a checker wouldn't be too hard. You'll need recursion. I'll leave that as an exercise for you or another SOer.

Answer 3

Maybe it's already answered enough, but let me add my shameless plug :) A JSON (actually any javascript object or array structure) diff & patch library I open sourced at github:

https://github.com/benjamine/jsondiffpatch

it generates diffs (also in JSON format, and with a small footprint), which you can use client (check the test page) & server side, and if present, it uses http://code.google.com/p/google-diff-match-patch/ for long strings automatically.

check the DEMO page to see how it works.

Answer 4

This did the trick for me when dealing with a similar problem. It gets the differences in second compared to first.

var first  = originalObj;
var second = modifiedObj;
var diff   = {};

var differ = function(first, second, result) {
    var i = 0;
    for (i in first) {
        if (typeof first[i] == "object" && typeof second[i] == "object") {
            result[i] = differ(first[i], second[i], {});
            if (!result[i]) delete result[i];
        } else if (first[i] != second[i]) {
            result[i] = second[i];
        }
    }
    return isEmpty(result) ? undefined : result;
}

differ(old_conf, new_conf, diff);

Code is a bit of a special case, but you get the general idea :P

Answer 5

You can use an object traversal module like nervgh/object-traverse to do this.

var result = {}
Object.traverse(old, function(node, value, key, path) {
  var resultObject = result
  for(var n=0; n<path.length-1; n++) {
    resultObject = resultObject[path[n]]
  }
  resultObject[key] = value
});