up vote 7 down vote favorite
6

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

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6 Answers

up vote 4 down vote accepted

You can iterate trough 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];
      }
    }
  }
}
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up vote 2 down vote

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

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up vote 2 down vote

I wrote this page to visualize the difference. The source is not minified if you want to check it out. http://jsondiff.com/

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up vote 1 down vote

Try http://prettydiff.com/ It is entirely written in JavaScript and works on both the client side and the server side. It is also algorithmic, so it can accurately diff between minified code and expanded code.

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up vote 1 down vote

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.

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+1 A sophisticated json diff algorithm, e.g. with string attributes, the decision whether to use the complete before and after string or do a diff inside the string, depending on the length of the resulting diff (I assume). – Eugene Beresovksy Aug 6 '12 at 10:28
Yes, a text diff is done when 2 long (how long is configurable) strings are found (in order to reduce diff size, and also to allow fuzzy patching). – Benja Aug 6 '12 at 14:57
up vote 1 down vote

did you look at : http://tlrobinson.net/projects/javascript-fun/jsondiff I think this is what you are looking for. :)

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the project seems to be gone – Eugene Beresovksy Aug 6 '12 at 10:30

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