setState 场景题

componentDidMount() {
  // count 初始值为 0
  this.setState({count: this.state.count + 1})
  console.log('1', this.state.count) // 0

  this.setState({count: this.state.count + 1})
  console.log('2', this.state.count) // 0

  setTimeout(() => {
    this.setState({count: this.state.count + 1})
    console.log('3', this.state.count) // 2
  })

  setTimeout(() => {
    this.setState({count: this.state.count + 1})
    console.log('4', this.state.count) // 3
  })

  // 1 0
  // 2 0 
  // 3 2
  // 4 3
}