extend/unextend objects

annotation.js

function e(
  a, // the source object
  b, // the target object to be extended
  c, // (placeholder)
  d  // (placeholder)
){
  b = b || this;       // extend the global object by default, and
  d = {};              // create a cache for the current objects.
                       
  for (c in a) {       // for each property on the target object,
    d[c] = b[c];       // save it on the cache object,
    b[c] = a[c]        // and replace it with the source object.
  };
  
  return {             // for hygiene's sake, return
    undo: function() { // an undo function
      e(d, b)          // that reverts the changes.
    }
  }
}

index.js

function e(a,b,c,d){b=b||this;d={};for(c in a){d[c]=b[c];b[c]=a[c]};return{undo:function(){e(d,b)}}}

LICENSE.txt

            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
                    Version 2, December 2004

 Copyright (C) 2011 Jed Schmidt <http://jed.is>

 Everyone is permitted to copy and distribute verbatim or modified
 copies of this license document, and changing it is allowed as long
 as the name is changed.

            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

  0. You just DO WHAT THE FUCK YOU WANT TO.

package.json

{
  "name":        "extend",
  "description": "extend/unextend object properties",
  "keywords":    ["extend", "object", "properties"]
}