Compare two objects properties in JS

Question

I need to compare two objects, and find out what properties are missing. The objects are fairly big, with several levels.

I will give short example of the type of object

Answer 1

If your situation allows it I'd suggest using http://underscorejs.org/ library, rather than rolling your own solution (or go look at their implementation). In JS deep object comparison is sometimes not trivial. If you decide to roll your own solution, you would recursively iterate through the properties and compare them one by one (ignoring native / built-in object properties and perhaps inherited from some prototype).

I'll gladly elaborate if you'd like.

Answer 2

function compare(base, compared, deepSearch) {
  var missing = [];

  var compareProp = function (baseValue, comparedValue, path, deepSearch) {
    //console.log('comparing', path.join('.'));

    if (comparedValue === undefined) {
      console.log('missing key', path.join('.'));

        if (!deepSearch) {
          return;
        }
    }

    if (typeof baseValue === 'object') {
      Object.keys(baseValue).forEach(function (key) {
        compareProp(baseValue [key], comparedValue && comparedValue [key], path.concat(key), deepSearch);
      }); 
    }
  };

  Object.keys(base).forEach(function (key) {
    compareProp(base [key], compared [key], [key], deepSearch);
  });
}

UC = {};
UC.start = {}
UC.start.enableHardEccDecline = '';
UC.start.template = {};
UC.start.template.ecc = '';
UC.start.template.decline = {};
UC.start.template.decline.title = '';
UC.start.template.decline.body = '';
UC.general = {};

compare (UC, {}, true);

Answer 3

I have just made a quick example here, not sure exactly how you want to apply this, but I have added the missing items to an array, which is logging it.

Obj1 should be your standard comparison object, obj2 the one received from request.

var obj1 = {};
obj1.test1 = 0;
obj1.test2 = 0;
obj1.test2222 = 0;
obj1.testLoremIpsum = 0;
obj1.lalala = 0;

var obj2 = {};
obj2.test1 = 0;
obj2.test25 = 0;
obj2.lalala1 = 0;

var k , i = 0;
var missingProps = [];

for( i in obj1 )
{
    var isFound = false;
    for( k in obj2) if( i == k ) isFound = true;
    if(!isFound) missingProps.push( i );
}
console.log(missingProps);

Answer 4

How about use JSON.stringify to convert object to string, then do the string comparison:

JSON.stringify(UC) === JSON.stringify(UCToBeCompared)

By using this method, you have to make sure the objects don't have circular reference, otherwise JSON.stringify would throw an exception

Answer 5

I have a made a example here. Hope it resolves your issue. It will compare Object KEYS only and return the object key which is not exist with compared object.

var a = Object.keys(obj1);
var b = Object.keys(obj2);

var missing= a.filter(function(v){
    return b.indexOf(v)==-1;
})

console.log(missing);