周遊小結

1.周遊數組下标

for(let i=0;i<=arr.length;i++){

console.log(i);           

}

for(let i in arr){

console.log(i);           

for(let i of arr.keys()){

console.log(i);           

2.周遊數組值

console.log(arr[i]);           

console.log(arr[i]);           

for(let m of arr){

console.log(m);           

}

for(let m of arr.values()){

console.log(m);           

3.周遊下标與值

console.log(i+':'+arr[i]);           

console.log(i+':'+arr[i]);           

for(let [p,q] of arr.entries()){

console.log(p+':'+q);           

4.forEach()用法：僅用于周遊純數組,參數為回調函數

arr.forEach(function(val,key){
console.log(key,val);           

});