简单的随机点名程序

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<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <meta http-equiv="X-UA-Compatible" content="ie=edge"> <title>随机点名</title> <style> #content{ width: 600px; height: 400px; background: #000; margin: 100px auto; text-align: center; position: relative; line-height: 300px; color: dodgerblue; font-size: 70px; } #btn1{ background: #ccc; width: 180px; height: 80px; font-size: 30px; color: #f40; border-radius: 12px; position: absolute; bottom: 30px; left: 50%; margin-left: -90px; } </style> </head> <body> <div id="content"> <span id="span1"> 点击开始 </span> <button id="btn1"> start </button> </div> <script> var arr = ['中国','英国','德国','美国','意大利','法国','西班牙','日本','阿联酋','荷兰','葡萄牙']; var $btn1 = document.getElementById('btn1'); var $content = document.getElementById('content'); var $span1 = document.getElementById('span1'); var timer;//计时器 var testNum = true; $btn1.onclick = function(){ if(testNum){ // console.log(1); start(); $btn1.innerHTML = 'stop'; testNum = false; } else{ // console.log(0); stop(); $btn1.innerHTML = 'start'; testNum = true; } } function start(){ timer = setInterval(function(){ var num = random(0,arr.length - 1); $span1.innerHTML = arr[num]; },50) } function stop(){ clearInterval(timer); } // 随机函数 function random(a,b){ var randomNum = Math.round(Math.random() * (b - a) + a); return randomNum; } </script> </body> </html>