js 中奖几率计算！

function getRand(obj){this.obj = obj;return this.init();}//获取几率总和getRand.prototype.sum = function(key){var self = this;var obj = this.obj;var sum=0;for(var i in obj){sum+=obj[i][key];}return sum;};//取得结果getRand.prototype.init = function(){var result = null;var self = this;var obj = this.obj;var sum = this.sum('prob');//几率总和for(var i in obj){var rand = parseInt(Math.random()*sum);if(rand<=obj[i].prob){result = obj[i];break;}else{sum-=obj[i].prob;}}return result;};//几率数组var obj = [{name:'广告一',prob:30},{name:'广告二',prob:18},{name:'广告三',prob:39},{name:'广告四',prob:60},{name:'广告五',prob:73},];//使用方法// $result = new getRand(obj);//测试数据，循环1000次取得每个数据出现的次数var record = [];for(var i = 0;i<1000;i++){var result = new getRand(obj);var index=false;for(var j in record){if(record[j].name==result['name']){index = j;break;}}if(index!==false){record[index].num+=1;}else{record.push({name:result['name'],num:1});}}console.log(record);

执行结果

0:{name: "广告五", num: 331}
1:{name: "广告四", num: 262}
2:{name: "广告三", num: 194}
3:{name: "广告一", num: 132}
4:{name: "广告二", num: 81}

参照网络php几率计算函数：

function get_rand($proArr) {   $result = '';   //概率数组的总概率精度   $proSum = array_sum($proArr);   //概率数组循环   foreach ($proArr as $key => $proCur) {     $randNum = mt_rand(1, $proSum);       //抽取随机数    if ($randNum <= $proCur) {       $result = $key;             //得出结果      break;     } else {       $proSum -= $proCur;               }   }   unset ($proArr);   return $result; }