//for循环顺序遍历

for (name in arr) {

console.log(`Hello, ${arr[name]}!`);

};

//while循环顺序遍历

var i = 0;

while (i<arr.length) {

console.log(`Hello, ${arr[i]}!`);

i = i + 1;

};

//do while循环逆序遍历

var j = arr.length - 1;

do {

console.log(`Hello, ${arr[j]}!`);

j = j - 1;

} while (j >= 0);