deepClone和白名单

深拷贝deepClone：

var obj = {
   name: 'David', 
   list: {
     age: 33
   }
 };
var d = _.deepClone(obj);
console.log(d);
console.log(d.list === obj.list);

_.deepClone = function(obj){
    //只支持array和object
    if (_.isArray(obj)) {
      return _.map(obj, function(elem){
        // 递归调用
        return _.isArray(elem) || _.isObject(elem) ? _.deepClone(elem) : elem;
      });
    }
    else if (_.isObject(obj)) {
      return _.reduce(obj, function(memo, value, key){
        memo[key] = _.isArray(value) || _.isObject(value) ? _.deepClone(value) : value;
        return memo;
      }, {});
    }
    return obj;
  };

白名单：

var d1 = _.pick({name: 'moe', age: 50, userid: 'moe1'}, 'name', 'age');
console.log(d1);
var d2 = _.pick({name: 'moe', age: 50, userid: 'moe1'}, function(value, key, object) {
  return _.isNumber(value);
});
console.log(d2);

 // 白名单
   _.pick = function(object, ointeratee, context) {
      var interatee, keys, target = {};
      if (!_.isObject(object)) {
         return object;
      }
      if (_.isFunction(ointeratee)) {
        keys = _.allKeys(object);
        interatee = optimizeCb(ointeratee, context);
      }
      else {
         keys = [].slice.call(arguments, 1);
         interatee = function(value, key, object) {
            return key in object;
         };
      }
      for (var i=0, len = keys.length; i < len; i++) {
        var key = keys[i];
        if (interatee(object[key], key, object)) {
           target[key] = object[key];
        }
      }
      return target;
 }

Note：
可以使用key in object来判断 object 上有没有属性key。

var d = {name: 'moe', age: 50, userid: 'moe1'};
console.log('name' in d);  // true
console.log('age' in d);   // true
console.log('gender' in d);// false