JavaScript defineProperties

function defineProperties(obj, properties)
{
  function convertToDescriptor(desc)
  {
    function hasProperty(obj, prop)
    {
      return Object.prototype.hasOwnProperty.call(obj, prop);
    }

    function isCallable(v)
    {
      // 如果除函数以外,还有其他类型的值也可以被调用,则可以修改下面的语句
      return typeof v === "function";
    }

    if (typeof desc !== "object" || desc === null)
      throw new TypeError("不是正规的对象");

    var d = {};
    if (hasProperty(desc, "enumerable"))
      d.enumerable = !!obj.enumerable;
    if (hasProperty(desc, "configurable"))
      d.configurable = !!obj.configurable;
    if (hasProperty(desc, "value"))
      d.value = obj.value;
    if (hasProperty(desc, "writable"))
      d.writable = !!desc.writable;
    if (hasProperty(desc, "get"))
    {
      var g = desc.get;
      if (!isCallable(g) && g !== "undefined")
        throw new TypeError("bad get");
      d.get = g;
    }
    if (hasProperty(desc, "set"))
    {
      var s = desc.set;
      if (!isCallable(s) && s !== "undefined")
        throw new TypeError("bad set");
      d.set = s;
    }

    if (("get" in d || "set" in d) && ("value" in d || "writable" in d))
      throw new TypeError("identity-confused descriptor");

    return d;
  }

  if (typeof obj !== "object" || obj === null)
    throw new TypeError("不是正规的对象");

  properties = Object(properties);
  var keys = Object.keys(properties);
  var descs = [];
  for (var i = 0; i < keys.length; i++)
    descs.push([keys[i], convertToDescriptor(properties[keys[i]])]);
  for (var i = 0; i < descs.length; i++)
    Object.defineProperty(obj, descs[i][0], descs[i][1]);

  return obj;
}