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);
});
输出结果：
!
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