How to deterministically verify that a JSON object hasn't been modified?

Question

According to MDN documentation for JSON.stringify:

Properties of non-array objects are not guaranteed to be stringified in any particular order. Do

Answer 1

These days I've been playing with the deterministic way to stringify an object and I've written the ordered object stringify to JSON, that solves the above noted dilemma: http://stamat.wordpress.com/javascript-object-ordered-property-stringify/

Also I was playing with custom hash table implementations which is also related to the topic: http://stamat.wordpress.com/javascript-quickly-find-very-large-objects-in-a-large-array/

//SORT WITH STRINGIFICATION

var orderedStringify = function(o, fn) {
    var props = [];
    var res = '{';
    for(var i in o) {
        props.push(i);
    }
    props = props.sort(fn);

    for(var i = 0; i < props.length; i++) {
        var val = o[props[i]];
        var type = types[whatis(val)];
        if(type === 3) {
            val = orderedStringify(val, fn);
        } else if(type === 2) {
            val = arrayStringify(val, fn);
        } else if(type === 1) {
            val = '"'+val+'"';
        }

        if(type !== 4)
            res += '"'+props[i]+'":'+ val+',';
    }

    return res.substring(res, res.lastIndexOf(','))+'}';
};

//orderedStringify for array containing objects
var arrayStringify = function(a, fn) {
    var res = '[';
    for(var i = 0; i < a.length; i++) {
        var val = a[i];
        var type = types[whatis(val)];
        if(type === 3) {
            val = orderedStringify(val, fn);
        } else if(type === 2) {
            val = arrayStringify(val);
        } else if(type === 1) {
            val = '"'+val+'"';
        }

        if(type !== 4)
            res += ''+ val+',';
    }

    return res.substring(res, res.lastIndexOf(','))+']';
}

Answer 2

Using Underscore or Lodash:

var sortByKeys = function(obj) {
  if (!_.isObject(obj)) {
    return obj;
  }
  var sorted = {};
  _.each(_.keys(obj).sort(), function(key) {
    sorted[key] = sortByKeys(obj[key]);
  });
  return sorted;
};

var sortedStringify = function() {
    arguments[0] = sortByKeys(arguments[0]);
    return JSON.stringify.apply(this, arguments);
};

Works in latest Chrome and Firefox.

JSFiddle here: http://jsfiddle.net/stchangg/ruC22/2/