react列表key满足这些条件可以直接使用数组索引

1. the list and items are static–they are not computed and do not change;
2. the items in the list have no ids;
3. the list is never reordered or filtered.

When all of them are met, you may safely use the index as a key.

参考：Index as a key is an anti-pattern (React) | by Robin Pokorny | Medium