Solved

Comparing Objects in JavaScript

Posted on 2009-07-07
8
1,112 Views
Last Modified: 2012-08-13
Hi Guys,

Does anyone have a good method that can returns true if all values in one object match that in another object? (it needs to support recursion too)

Ex:
var o1 = {
  item1:123
  item2: {
    item3: 456
  }
}
var o2 = {
  item1:123
  item2: {
    item3: 456
  }
}
var o3 = {
  item1:123
  item2: {
    item3: 'ABC'
  }
}

So when comparing o1 to o2 the method would eval to true, comparing o1 to o3 would eval to false.

Cheers,
Dan
0
Comment
Question by:dancablam
  • 5
  • 2
8 Comments
 
LVL 41

Expert Comment

by:HonorGod
ID: 24798729
That might be difficult.  Consider the scenario where the object contains a "this" reference.
The eval would only be able to return true if the objects being compared refer to a single object.
0
 
LVL 41

Expert Comment

by:HonorGod
ID: 24798759
A simple test to see if two variables reference the same object would be to use the === operator.


function same( a, b ) {
  return a === b;
}

Open in new window

0
 
LVL 3

Author Comment

by:dancablam
ID: 24798823
The objects will only contain data - not methods. Also they won't be referencing the same object so the === won't work. I simply need a method to walk recursively down an object and see if all the property/value combinations match.
0
Free Tool: IP Lookup

Get more info about an IP address or domain name, such as organization, abuse contacts and geolocation.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

 
LVL 3

Expert Comment

by:laneway
ID: 24798892
This will work for objects that both have the same values:
function compareObj(obj1,obj2) {
    // if obj1 and obj2 are not both objects, return simple comparison
    if (typeof obj1 != 'object' || typeof obj2 != 'object') { return (obj1==obj2); }
    // compare indexes in obj1 with those in obj2
    for (index in obj1) {
      var item1 = obj1[index];
      var item2 = obj2[index];
      if (typeof item1 == 'object') if (!compareObj(item1,item2)) return false;
      if (typeof item1 != 'object') if (item1!=item2) return false;
    }
    // if we got this far, the are the same
    return true;
} 
 
// demo
var o1 = { item1:123, item2: { item3: 456 } };
var o2 = { item1:123, item2: { item3: 456 } };
var o3 = { item1:123, item2: { item3: 'ABC' } };
alert(compareObj(o1,o2));
alert(compareObj(o1,o3));

Open in new window

0
 
LVL 3

Expert Comment

by:laneway
ID: 24798913
Clarification. The above code will work for objects that both have the same properties. Example:
// comparing these two will work
var o1 = { item1:'abc' }
var o2 = { item1:'def' }
// but comparing these two won't always work properly
var o1 = { item1:'abc' }
var o2 = { item1:'def',item2:'xyz' }

Open in new window

0
 
LVL 41

Expert Comment

by:HonorGod
ID: 24798981
Something like this perhaps?
<html>
<body>
 
<script type="text/javascript">
var o1 = {
  item1 : 123,
  item4 : 'Hi',
  item2 : { item3 : 456 }
}
var o2 = {
  item1 : 123,
  item4 : 'hi',
  item2 : { item3 : 456 }
}
var o3 = {
  item1 : 123,
  item4 : 'Hi',
  item2 : { item3 : 'ABC' }
}
 
function oCompare( o1, o2 ) {
  var result = false;
  if ( typeof( o1 ) == typeof( o2 ) ) {
    if ( typeof( o1 ) == 'object' ) {
      if ( o1 === o2 ) {
        return true;
      } else {
        for ( p in o1 ) {
          if ( p in o2 ) {
            var T = typeof( o1[ p ] );
            if ( T == typeof( o2[ p ] ) ) {
              switch ( T ) {
                case 'boolean' : if ( o1[ p ] != o2[ p ] ) return false;
                  break;
                case 'number' : if ( o1[ p ] != o2[ p ] ) return false;
                  break;
                case 'function' : if ( o1[ p ] !== o2[ p ] ) return false;
                  break;
                case 'string' : if ( o1[ p ] != o2[ p ] ) return false;
                  break;
                case 'object' : if ( !oCompare( o1[ p ], o2[ p ] ) ) return false;
                  break;
                default:
                  alert( 'p: ' + p + ' typeof: ' + T );
              }
            } else {
              return false;
            }
          } else {
            return false;
          }
        }
      }
    }
  }
  return result;
}
 
document.write( oCompare( o1, o3 ) );
 
</script>
 
</body>
</html>

Open in new window

0
 
LVL 41

Accepted Solution

by:
HonorGod earned 500 total points
ID: 24799040
nope, not quite...

We also have to check that all properties in object2 exist and are the same as found in object1...
<html>
<body>
 
<script type="text/javascript">
var o1 = {
  item1 : 123,
  item4 : 'Hi',
  item2 : { item3 : 456 }
}
var o2 = {
  item1 : 123,
  item4 : 'Hi',
//item5 : true,
  item2 : { item3 : 456 }
}
var o3 = {
  item1 : 123,
  item4 : 'Hi',
  item2 : { item3 : 'ABC' }
}
 
function oCompare( o1, o2 ) {
  if ( typeof( o1 ) == typeof( o2 ) ) {
    if ( typeof( o1 ) == 'object' ) {
      if ( o1 === o2 ) {
        return true;
      } else {
        for ( p in o1 ) {
          if ( p in o2 ) {
            var T = typeof( o1[ p ] );
//          alert( p + ' ' + o1[ p ] + ' ' + o2[ p ] );
            if ( T == typeof( o2[ p ] ) ) {
              switch ( T ) {
                case 'boolean' : if ( o1[ p ] != o2[ p ] ) return false;
                  break;
                case 'number' : if ( o1[ p ] != o2[ p ] ) return false;
                  break;
                case 'function' : if ( o1[ p ] !== o2[ p ] ) return false;
                  break;
                case 'string' : if ( o1[ p ] != o2[ p ] ) return false;
                  break;
                case 'object' : if ( !oCompare( o1[ p ], o2[ p ] ) ) return false;
                  break;
                default:
//                alert( 'p: ' + p + ' typeof: ' + T );
              }
            } else {
              return false;
            }
          } else {
            return false;
          }
        }
      }
    }
  }
  return true;
}
 
document.write( oCompare( o1, o2 ) && oCompare( o2, o1 ) );
 
</script>
 
</body>
</html>

Open in new window

0
 
LVL 41

Expert Comment

by:HonorGod
ID: 24842512
Thanks for accepting my solution.

I'm sorry that you didn't feel that it was worthy of an A.

Good luck & have a great day.
0

Featured Post

Free Tool: Port Scanner

Check which ports are open to the outside world. Helps make sure that your firewall rules are working as intended.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
Button and js nou working 3 20
Not allowed to load local recource. 4 35
how can i get 4 nd 5 ? 3 31
Make Session back to empty 9 30
Today I would like to talk about localizing (Internationalization) JavaScript applications. Introduction When creating an application that is going to be used by many people around the globe, it is important to remember that not everyone speak…
Today, the web development industry is booming, and many people consider it to be their vocation. The question you may be asking yourself is – how do I become a web developer?
The viewer will learn the basics of jQuery, including how to invoke it on a web page. Reference your jQuery libraries: (CODE) Include your new external js/jQuery file: (CODE) Write your first lines of code to setup your site for jQuery.: (CODE)
The viewer will learn the basics of jQuery including how to code hide show and toggles. Reference your jQuery libraries: (CODE) Include your new external js/jQuery file: (CODE) Write your first lines of code to setup your site for jQuery…

837 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question