content: import React from 'react'
  
  class B extends React.Component {
      constructor (props) {
          super(props)
          this.handleClickOne = this.handleClickOne.bind(this)
          this.handleClickFour = ::this.handleClickFour
          function map(func) {
              var mapped = new Array(this.length);
              for(var i = 0; i < this.length; i++) {
                  mapped[i] = func(this[i], i);  
              }
              return mapped;
          }
          console.log([1, 2, 3]::map(x => x * 2))
      }
  
      handleBack () {
          history.back()
      }
  
      handleClickOne () {
          alert('点击一')
          console.log('使用   this.handleClickOne = this.handleClickOne.bind(this)')
      }
  
      handleClickTwo () {
          alert('点击二')
          console.log('使用   this.handleClickFour = ::this.handleClickFour')
      }
  
      handleClickThree = () => {
          alert('点击三')
          console.log('使用   handleClickThree = () => {alert("点击三")}')
      }
  
      handleClickFour () {
          alert('点击四')
          console.log('使用   this.handleClickFour = ::this.handleClickFour')
      }
  
      render () {
          return(<div className="detail">
          <div className="nav"><span className="nav-back" onClick={ () => this.handleBack() }> 《 返回</span></div>
          <div className="content">
          <p>
              <button onClick={this.handleClickOne}>点击一</button>
              <br /><br />
              <button onClick={ () => this.handleClickTwo()}>点击二</button>
              <br /><br />
              <button onClick={this.handleClickThree}>点击三</button>
              <br /><br />
              <button onClick={this.handleClickFour}>点击四</button>
              <br /><br />
          </p>
          </div>
          </div>);
      }
  }
  
  export default B