| 12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455 | <!DOCTYPE html><html lang="en"><head>  <meta charset="UTF-8">  <meta http-equiv="X-UA-Compatible" content="IE=edge">  <meta name="viewport" content="width=device-width, initial-scale=1.0">  <title>Document</title></head><body>  <button id="btn">按钮</button>  <button id="stop">按钮B</button>  <button id="num">按钮C</button>  <script>    var btn = document.getElementById('btn')    var stop = document.getElementById('stop')    var num = document.getElementById('num')    /* 间隔多少毫秒去执行 */    btn.onclick = function () {      var b = 1      var a = setInterval(function () {        if (b < 10) {          b++          console.log(b)        } else {          clearInterval(a)        }      }, 1000)    }    stop.onclick = function () {      var c = setTimeout(function () {        console.log(111)      }, 1000)    }    /*      setInterval   不断的去执行   通过clearInterval 清除定时器    setTimeout   只执行一次 */    num.onclick = function () {      //获取一个随机数      //Math.random()  0~1      //Math.floor  向下取整  跟四舍五入没关系         var h = setInterval(function () {        var nn = Math.random() * 10        var mm = Math.floor(nn)        console.log(mm)      }, 1000)    }  </script></body></html>
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