Minimalist extend function

extend.js

function extend(destination) { 
  var prop, source;
  var index = 0;
  var length = arguments.length;

  while (++index < length) {
    source = arguments[index];

    for (prop in source) {
      destination[prop] = source[prop];
    }
  }

  return destination;
}

Thanks jdiddy!