js中几种遍历对象的方法，包括for.of、for

js中几种遍历对象的方法，包括for..of、for..in、Object.keys、Object.getOwnProperty,它们在使用场景方面各有不同。

js对象的属性中可直接用、可访问到的属性分为数据属性和访问器属性。

数据属性（实际存储属性值的属性）的四大特性：

{

        value: 属性值,    
        writable: true/false,  //控制是否可修改    
        enumerable: true/false, //控制是否可被for in遍历    
        configurable: true/false, //1. 控制是否可删除 2. 控制是否可修改前两个特性  3.一旦改为false不可逆                                                       
    }

访问器属性（不实际存储数据，专门提供对其它数据/变量的保护）的四大特性：

{

        get:function(){return this.隐藏属性;},
        set:function(val){
            //如果val符合条件
                this.隐藏属性=val
            //否则
                报错
        },
        enumerable, configurable

for..in

返回的是所有能够通过对象访问的、可枚举的属性，既包括存在于实例中的属性，也包括存在于原型中的实例,不能保证属性按对象原来的顺序输出。（可枚举-自身-原型）

var obj = {a:1, b:2, c:3};

        
    for (var prop in obj) {
      console.log("obj." + prop + " = " + obj[prop]);
    }
    // Output:
    // "obj.a = 1"
    // "obj.b = 2"

Object.keys

用于获取对象自身所有的可枚举的属性值，但不包括原型中的属性，然后返回一个由属性名组成的数组。注意它同for..in一样不能保证属性按对象原来的顺序输出。（可枚举-自身）

// 数组

    var arr = ['a', 'b', 'c'];
    console.log(Object.keys(arr)); // console: ['0', '1', '2']
    // 类数组对象
    var obj = { 0: 'a', 1: 'b', 2: 'c' };
    console.log(Object.keys(obj)); // console: ['0', '1', '2']
    // 类数组对象-随机下标
    var anObj = { 100: 'a', 2: 'b', 7: 'c' };
    console.log(Object.keys(anObj)); // console: ['2', '7', '100']
    // 不可枚举属性getFoo
    var myObj = Object.create({}, {
      getFoo: {
        value: function () { return this.foo; }
      } 
    });
    myObj.foo = 1;

Object.getOwnProperty

如果你想获取一个对象的所有属性js map 遍历对象数组，甚至包括不可枚举的，则可用该方法。其返回对象的所有自身属性的属性名组成的数组，但不会获取原型链上的属性。（可枚举&不可枚举-自身）

//获取不可枚举属性

    var my_obj = Object.create({}, {
      getFoo: {
        value: function() { return this.foo; },
        enumerable: false
      }
    });
    my_obj.foo = 1;

下面的例子演示了该方法不会获取到原型链上的属性：

function ParentClass() {}

    ParentClass.prototype.inheritedMethod = function() {};
    function ChildClass() {
      this.prop = 5;
      this.method = function() {};
    }
    ChildClass.prototype = new ParentClass;
    ChildClass.prototype.prototypeMethod = function() {};
    console.log(
      Object.getOwnPropertyNames(
        new ChildClass()  // ["prop", "method"]
      )

for..of

es6新增方法，主要来遍历可迭代的对象（包括Array, Map, Set, arguments等），它主要用来获取对象value值，而for..in主要获取对象key值。

另外：可以由break, continue, throw 或return终止。在这些情况下，迭代器关闭。

let iterable = [10, 20, 30];

    for (let value of iterable) {
        value += 1;
        console.log(value);
    }
    // 11
    // 21

与for..in循环之间的区别：

Object.prototype.objCustom = function() {};

    Array.prototype.arrCustom = function() {};
    let iterable = [3, 5, 7];
    iterable.foo = 'hello';
    for (let i in iterable) {
      console.log(i); //  0, 1, 2, "foo", "arrCustom", "objCustom"
    }
    for (let i in iterable) {
      if (iterable.hasOwnProperty(i)) {
        console.log(i); //  0, 1, 2, "foo"
      }
    }
    for (let i of iterable) {
      console.log(i); //  3, 5, 7

小结

其实这几个方法之间的差异主要在属性是否可可枚举js map 遍历对象数组，是来自原型，还是实例。

开发中的实际应用

需求：将如下两个从后台不同端口获取的json对象数组整合处理成如下注释部分的json对象

var goodsSpecJSON = [{

                    "SpecA": "颜色"
                }, {
                    "SpecB": "容量"
                }, {
                    "SpecC": "大小"
                }, {
                    "SpecD": "尺寸"
                }, {
                    "SpecE": "套餐"
                }];
    var goodsSpecList = [{
        c_id: 3133,
        costPrice: 0,
        discountPrice: 0,
        earn: 0,
        etime: null,
        flag: 0,
        goodsDetailCount: 199,
        goodsDetailId: "100PgQ2xy08121409mY27",
        goodsDetailInventory: 199,
        goodsDetailOff: 0,
        goodsDetailPic: "/upload/messageImage/1523281057461_Personal.jpg,/upload/messageImage/1523282906972_Personal.jpg,/upload/messageImage/1523283570897_Personal.jpg",
        goodsDetailPrice: 188,
        goodsDetailSpec: "",
        goodsId: "00Y1kR4r1029X822731o0",
        isHost: 0,
        managerEarn: 0,
        postage: 10,
        profit: 0,
        specA: "红色",
        specB: "32G",
        specC: "小",
        specD: "4.7寸",
        specE: "套餐一",
        unionEarn: 0,
        vipPrice: 0
    }, {
        c_id: 3134,
        costPrice: 0,
        discountPrice: 0,
        earn: 0,
        etime: null,
        flag: 0,
        goodsDetailCount: 199,
        goodsDetailId: "100PgQ2xy08121409mY27",
        goodsDetailInventory: 199,
        goodsDetailOff: 0,
        goodsDetailPic: "/upload/messageImage/1523281057461_Personal.jpg,/upload/messageImage/1523282906972_Personal.jpg,/upload/messageImage/1523283570897_Personal.jpg",
        goodsDetailPrice: 188,
        goodsDetailSpec: "",
        goodsId: "00Y1kR4r1029X822731o0",
        isHost: 0,
        managerEarn: 0,
        postage: 10,
        profit: 0,
        specA: "白色",
        specB: "64G",
        specC: "小",
        specD: "5寸",
        specE: "套餐二",
        unionEarn: 0,
        vipPrice: 0
    }, {
        c_id: 3135,
        costPrice: 0,
        discountPrice: 0,
        earn: 0,
        etime: null,
        flag: 0,
        goodsDetailCount: 199,
        goodsDetailId: "100PgQ2xy08121409mY27",
        goodsDetailInventory: 199,
        goodsDetailOff: 0,
        goodsDetailPic: "/upload/messageImage/1523281057461_Personal.jpg,/upload/messageImage/1523282906972_Personal.jpg,/upload/messageImage/1523283570897_Personal.jpg",
        goodsDetailPrice: 188,
        goodsDetailSpec: "",
        goodsId: "00Y1kR4r1029X822731o0",
        isHost: 0,
        managerEarn: 0,
        postage: 10,
        profit: 0,
        specA: "黑色",
        specB: "128G",
        specC: "小",
        specD: "4.7寸",
        specE: "套餐一",
        unionEarn: 0,
        vipPrice: 0
    }, {
        c_id: 3136,
        costPrice: 0,
        discountPrice: 0,
        earn: 0,
        etime: null,
        flag: 0,
        goodsDetailCount: 199,
        goodsDetailId: "100PgQ2xy08121409mY27",
        goodsDetailInventory: 199,
        goodsDetailOff: 0,
        goodsDetailPic: "/upload/messageImage/1523281057461_Personal.jpg,/upload/messageImage/1523282906972_Personal.jpg,/upload/messageImage/1523283570897_Personal.jpg",
        goodsDetailPrice: 188,
        goodsDetailSpec: "",
        goodsId: "00Y1kR4r1029X822731o0",
        isHost: 0,
        managerEarn: 0,
        postage: 10,
        profit: 0,
        specA: "蓝色",
        specB: "64GG",
        specC: "大",
        specD: "4.5寸",
        specE: "套餐二",
        unionEarn: 0,
        vipPrice: 0
    }];
    // var keys = {
    //     '颜色': ['红色', '白色'],
    //     '容量': ['8g', '16g', '32g', '64g'],
    //     '尺寸': ['大', '小', '大'],
    //     '套餐': ['套餐一', '套餐二', '套餐三']
    // };
    // //SKU，Stock Keeping Uint(库存量单位)    
    // var sku_list = [{
    //     'attrs': '红色|16g|big|套餐二',
    //     'price': 120
    // }, {
    //     'attrs': '红色|8g|big|套餐一',
    //     'price': 10
    // }, {
    //     'attrs': '白色|16g|big|套餐二',
    //     'price': 28
    // }, {
    //     'attrs': '红色|64g|small|套餐三',
    //     'price': 220
    // }, {
    //     'attrs': '白色|32g|middle|套餐二',
    //     'price': 130
    // }, {
    //     'attrs': '红色|32g|big|套餐一',
    //     'price': 120

实现：主要利用Object.keys方法获取对象的key,value值，配上forEach循环实现最终想要的结果。

var keys = {};

    var sku_list = [];
    //原数据转换小写
    goodsSpecJSON = goodsSpecJSON.map(function (keyo) {
        var key = Object.keys(keyo)[0];
        var newkey = key.substring(0, 1).toLowerCase() + key.substring(1);
        var dic = {};
        dic[newkey] = keyo[key];
        return dic
    });
    //生成keys
    goodsSpecJSON.forEach(function (keyo) {
        var key = Object.keys(keyo)[0]; //['specA']
        var val = keyo[key]; //颜色
        if (!keys.hasOwnProperty(val)) {
            keys[val] = [];
        }
        var hash = {};
        goodsSpecList.forEach(function (item, i) {
            if (hash[item[key]] === undefined) {
                hash[item[key]] = true;
                keys[val].push(item[key]);
            }
            // if (keys[val].indexOf(item[key]) === -1) {
            //     keys[val].push(item[key]);
            // }
        });
    });
    console.log(keys)
    //生成sku_list
    goodsSpecList.forEach(function (item) {
        var dic = {
            attrs: ''
        };
        goodsSpecJSON.forEach(function (keyo, j) {
            var key = Object.keys(keyo)[0];
            dic.attrs += item[key] + (j === goodsSpecJSON.length - 1 ? '' : '|');
            dic.price = item.goodsDetailPrice;
            dic.goodsDetailCount = item.goodsDetailCount;
            dic.goodsDetailId = item.goodsDetailId;
        });
        sku_list.push(dic);
    });