Common methods for JS to traverse arrays and objects?

Here is a summary of several commonly used arrays and object traversal methods

object:

The first type: for...in 

var obj={"G":"good","B":"bad","E":"erro"};
for(var index in obj){

console.log("key:",index,"value:",obj[index])

}

result:

 

The second type: Object.keys()

var obj={"G":"good","B":"bad","E":"erro"};
var arr=Object.keys(obj)
arr.forEach(item=>{
    console.log("key:",item,"value:",obj[item])
})

result:

array:

The first type: forEach

var arr=["今天","明天","后天"]
arr.forEach((value, index)=>{
  console.log('value:', value, 'index:', index);
})

result:

The second type: map

var arr=["今天","明天","后天"]
arr.map((item,index)=>{
     console.log('value:', item, 'index:', index);
})

result:

For loop traversal: for, for...in, for...of are written together
 

var arr=["今天","明天","后天"]
for (var i = 0; i < arr.length; i++) {
  console.log("for遍历",'index:',i,'value:', arr[i])
}
for (var i in arr) {
  console.log("for...in遍历",'index:', i, 'value:', arr[i])
}
for (var value of arr) {
  console.log("for...of遍历",'value', value)
}

 result: