<script>
        const startBtn = document.getElementById('start')
        const stopBtn = document.getElementById('stop')
        const box = document.getElementById('box')
        var show = {
            content: "Hello World",
            timer: null,
            start: function () {
                // 在此补充代码
                startBtn.onclick=()=>{
                    this.timer=setInterval(()=>{
                        box.innerHtml+=this.content;
                    },1000)
                }
            },
            stop: function () {
                在此补充代码
              stopBtn.onclick=()=>{
                  clearInterval(this.timer)
              }

            }
        }
         // 在此补充代码
        show.start();
        show.stop();
    </script>

​