事件冒泡，事件捕获和事件委托

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    document.getElementById(‘parent‘).addEventListener(‘click‘,function(e){
      console.log(e)
      console.log(this.id + ‘被触发‘)

    },true);
    document.getElementById(‘child‘).addEventListener(‘click‘, function(e){
      console.log(e)
      console.log(this.id + ‘被触发‘)
    },true
    )