深拷贝函数

针对js中的各种数据类型（String, Number, Boolean, Array, Object)进行深度拷贝：

function clone(obj){
  var type = typeof (obj);
  if (type === "string" || type === "boolean" || type === "number") {
    var newone = obj;
  } else if (type === "object") {
    if (obj === null) {
      var newone = null;
    } else if (Object.prototype.toString.call(obj).slice(8,-1) === "Array") {
    //  Object.prototype.toString.call([1,2,3])的返回值为"[object Array]"
      var newone = [];
      for (var i=0; i<obj.length; i++) {
        newone.push(clone(obj[i]));
      }
    } else if (Object.prototype.toString.call(obj).slice(8,-1) === "Object") {
      var newone = {};
      for (var i in obj) {
        newone[i] = clone(obj[i]);
      }
    }
  }
  return newone;
}

**
注意 Object.prototype.toString.call(obj)用法