mutations

• 用来修改state的函数
• 只能是同步的，不能是异步的

调用该函数

• commit(对应函数名)

实例

You can pass an additional argument to store.commit, which is called the payload for the mutation:

// ...
mutations: {
  increment (state, n) {
    state.count += n
  }
}

store.commit('increment', 10)

In most cases, the payload should be an object so that it can contain multiple fields, and the recorded mutation will also be more descriptive:

// ...
mutations: {
  increment (state, payload) {
    state.count += payload.amount
  }
}

store.commit('increment', {
  amount: 10
})