沐游虞的博客

这一段会输出什么值呢？let arr = [1, 2, 0, 3]for (let i = 0, val; val = arr[i++]; ) { // ...}答案：只会输出1和2。原因：当i=2的时候取出来的值是0,ta是会被判定为false的，所以就退出循环。如何解决这种情况呢，自己手写判断条件。let arr = [1, 2, 0, 3]for (let i = 0, val; ; ) { val = arr[i++] if (val === undefined

报错详情如下Error: Element type is invalid: expected a string (for built-in components) or a class/function (for composite components) but got: undefined. You likely forgot to export your component from the file it's defined in, or you might have mixed up