Simple inheritance model for JavaScript

gistfile1.js

function extend(p, c)
{
  var f = function() {};
  f.prototype = p.prototype;
  c.prototype = new f();
  c.prototype.constructor = c;
}

function mixin(p, c)
{
  if(arguments.length > 2)
  {
    for(var i = 2, j = arguments.length; i < j; i++)
    {
      c.prototype[arguments[i]] = p.prototype[arguments[i]]
    }
  }

  else
  {
    for(m in p.prototype)
    {
      if(!c.prototype[m]) c.prototype[m] = p.prototype[m]
    }
  }
}