diff.js

// By weepy 
function diff(b,a) {

 var d={}

 // additions
 var tb = typeOf(b)
 var ta = typeOf(a)
 if(ta != tb)
   return b


 if(typeOf(b) == "number" || typeOf(a) == "string") {
   if(b==a)
     return undefined
   else
     return b
 }


 for(i in b ) {
   var x = b[i]
   var y = a[i]
   var tx = typeOf(x)
   var ty = typeOf(y)

   if(x==y)
     continue
   if(tx == ty) {
     if(tx=="number" || tx=="string") {
       d[i] = x
     } else {
       var i = diff(x,y)
       if(!is_empty(i))
         d[i] = i
     }
   } else {
      // changed types
      d[i] = x
   }
 }

       // removals
       for(i in a) {
   var x = b[i]
   var y = a[i]
               if(y && !x)
                 d[i] = null
 }

 if(is_empty(d))
   return null

       return d
}

function is_empty(obj) {
 for(var i in obj)
   return false
 return true
}

function typeOf(value) {
   var s = typeof value;
   if (s === 'object') {
       if (value) {
           if (typeof value.length === 'number' &&
                   !(value.propertyIsEnumerable('length')) &&
                   typeof value.splice === 'function') {
               s = 'array';
           }
       } else {
           s = 'null';
       }
   }
   return s;
}

//diff([1,2,3],[1,2,4]) => {2:3}
//diff([1,2,3],[1,2,3]) => null
//diff({a:1,b:2},{a:1}) => {b:2}
//diff({a:1},{a:2}) => {a:1}
//diff({a:1, b: {c:2,d:4} },{a:1 , b : {c:2} }) => { "[object Object]" => {d:4} }