es6 代码片段理解

代码片段理解：

[INCREMENT]: (state, action) => {
    const { payload: { id } } = action

    //because payload contains the id and we already know that we are about
    //to increment the value of that id, we modify only that value by one

    return {
      ...state,
      counters: {
        ...state.counters,
        [id]: state.counters[id] + 1
      }
    }
  },

line 2:

const { payload: { id } } = action
相当于： id = action.payload.id

line 8 - 10:

{
 8       ...state,
 9       counters: {
10         ...state.counters,
11         [id]: state.counters[id] + 1
12       }
13     }

是表达：state.counter[id] =  state.counters[id] + 1