抽奖概率

来源：互联网发布：sql 字符串函数编辑：程序博客网时间：2024/04/29 09:14
<!doctype html><html><head lang="zh">    <meta charset="utf-8">    <title>灵域</title>    <meta name="renderer" content="webkit"><body><input type="button" value="10000" id="input1"><h1>一等奖:5‰,二等奖:3%,三等奖:80%,纪念奖(谢谢惠顾)</h1><ul><li>一等奖 : <span></span></li>    <li>二等奖 : <span></span></li>    <li>三等奖 : <span></span></li>    <li>纪念奖 : <span></span></li></ul><script>var oInput = document.getElementById('input1');var aSpan = document.getElementsByTagName('span');var size = 1000;var arr1 = [0.005*size , 0.03*size , 0.8 * size];var arr2 = [];var num = 0;oInput.onclick = function(){arr2=[];num = 0for(var i =0; i< arr1.length; i++){var iNow = 0;num += arr1[i];arr2.push({iNow:0,val:num})}var fre = parseInt(oInput.value);var sum = 0;for(var i=0; i< fre; i++){var val = Math.random()*size;fnCount(val);}for(var i=0;i<aSpan.length;i++){//没中奖的，将前面的累加if(aSpan.length-1 == i){aSpan[i].innerHTML = fre - sum;}//中奖的else{aSpan[i].innerHTML = arr2[i].iNow;sum += arr2[i].iNow;}}}function fnCount(val){for(var i=0;i<arr2.length;i++){if(arr2[i].val > val){arr2[i].iNow++;break;}}}</script></body></html>
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