ES6為我們提供了for-in循環(huán)和for-Each循環(huán)還要強(qiáng)大

之前的for-in循環(huán)

var arr=['apple','orange','banana','strawberry'];
for (var i in arr) { 
  console.log(i);
}
//打印的是索引值
0,1,2,3

for-of循環(huán)

遍歷數(shù)組

var arr=['apple','orange','banana','strawberry'];
for (var i in arr) { 
  console.log(i);
}
//打印的是每一項(xiàng)的值
apple
orange
banana
strawberry

也可以遍歷字符串

var string = "boa";

for (var value of string) {
    console.log(value);
}

// "b"
// "o"
// "o"

遍歷Map對(duì)象

let iterable = new Map([["a", 1], ["b", 2], ["c", 3]]);

for (let entry of iterable) {
  console.log(entry);
}
// [a, 1]
// [b, 2]
// [c, 3]

for (let [key, value] of iterable) {
  console.log(value);
}
// 1
// 2
// 3