JS遍历对象和数组

遍历对象：

1.利用Objects.keys方法：

var obj = {'0':'a','1':'b','2':'c'};
Object.keys(obj).forEach((key)=>{
     console.log(key,obj[key]);
});
0 a
1 b
2 c

今天遇到一个前端界面渲染的问题，用forEach无法得到结果

用map好像可以达到和上面同样的效果

var obj = {'0':'a','1':'b','2':'c'};
Object.keys(obj).map((key)=>{
     console.log(key,obj[key]);
});

 

2.for

var obj = {'0':'a','1':'b','2':'c'};
for(var i in obj) {
     console.log(i,obj[i]);
}
0 a
1 b
2 c

3.

var obj = {'0':'a','1':'b','2':'c'};
Object.getOwnPropertyNames(obj).forEach(function(key){
    console.log(key,obj[key]);
});
0 a
1 b
2 c

4.

var obj = {'0':'a','1':'b','2':'c'};
Reflect.ownKeys(obj).forEach(function(key){
   console.log(key,obj[key]);
});
0 a
1 b
2 c

遍历数组

1.map方法：

var obj = ["lijun",2,3,4,5];
obj.map((item,index)=>{//第一个参数值，第二个参数下标
  console.log(index,item);
})
0 "lijun"
1 2
2 3
3 4
4 5

2.for in

var obj = ["lijun",2,3,4,5];
for (var i in obj){
  console.log(i,obj[i]);
}

3.for of主要获取值

var obj = ["lijun",2,3,4,5];
for (var value of obj){
    console.log(value);
}

4.foreach

var obj = ["lijun",2,3,4,5];
obj.forEach((item, index)=>{
  console.log(index, item);
});