setState function

Question

以下官方对setState的解释怎么理解呢？和多个state顺序改变有什么关系呀

"It's also possible to pass a function with the signature function(state, props) => newState. This enqueues an atomic update that consults the previous value of state and props before setting any values. For instance, suppose we wanted to increment a value in state by props.step:"

Answer 1

也可以以 function(state, props) 传递一个函数。当你想要把一个在设置任何值之前参考前一次 state+props 的值的原子更新放在队列中 这会有很用。例如，假如我们想在 state 增加一个值: