那里您的代码中有轻微的混淆

there is slight confusion in your code

 componentDidMount(){
      window.addEventListener("resize", this.updateDimensions.bind(this)); 
      // first instance listening to event
    }
    componentWillUnmount(){
      console.log("unmounting....");
      window.removeEventListener('resize', this.updateDimensions.bind(this));
      // second instance removed from listener here first!== second
    }

试试这个

 constructor(props) {
      super(props);
      this.updateDimensions = this.updateDimensions.bind(this);
    }
    componentDidMount(){
      window.addEventListener("resize", this.updateDimensions);
      // first instance listening to event
    }
    componentWillUnmount(){
      console.log("unmounting....");
      window.removeEventListener('resize', this.updateDimensions);
      // same instance removed from listener here first == second
    }