阻断setTimeOut.html

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    <head>
        <meta charset="utf-8">
        <meta http-equiv="X-UA-Compatible" content="IE=edge">
        <title></title>
        <meta name="description" content="">
        <meta name="viewport" content="width=device-width, initial-scale=1">
        <link rel="stylesheet" href="">
    </head>
    <body>
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         <div id='box'>
1
         </div>   
        <button id='btn1' >2S后变色</button>
        <button id=btn2>阻断</button>
        <script>
            window.onload=()=>{
                let box = document.querySelector('#box')
                // function hanldeStart(){
                //     box.style.backgrandColor='red'
                // }           
                let timer ;
                btn1.addEventListener('click',()=>{         
                    if(timer){
                        return
                    }
                    timer = setTimeout(()=>{
                         console.log(timer)
                         box.style.backgroundColor='red' 
                    },2000)
                })
                btn2.addEventListener('click',()=>{         
                    if(timer){
                        clearTimeout(timer)
                        timer = null
                        console.log(timer)
                    }
                })
            }
        </script>
    </body>
</html>