1,先看for in的用法
var obj = {a:1, b:2, c:3};
for (var prop in obj) {
console.log(prop);
}
// 打印结果 a, b, c
var obj = ['a', 'b', 'c'];
for (var prop in obj) {
console.log(prop);
}
// 打印结果 0,1,2
由此可见,for in 能遍历对象或数组的属性
2,接下来是 for of
var a = [{a:1}, {b:2}, {c:3}];
for(let val of a) {
console.log(val);
}
// 打印结果,{a:1}, {b:2}, {c:3}
由此可见,for of能遍历出数组的值