js数组实现权重概率分配，支持数字比模式(支持2位小数)和百分比模式(不支持小数，最后一个元素多退少补)

@param Array arr js数组，参数类型[Object,Object……]

@return Array 返回一个随机元素，概率为其weight/所有weight之和，参数类型Object

@author shuiguang
*/
function weight_rand(arr){
//参数arr元素必须含有weight属性，参考如下所示
//var arr=[{name:'1',weight:1.5},{name:'2',weight:2.5},{name:'3',weight:3.5}];
//var arr=[{name:'1',weight:'15%'},weight:'25%'},weight:'35%'}];
//求出最大公约数以计算缩小倍数，perMode为百分比模式
var per;
var maxNum = 0;
var perMode = false;
//自定义Math求最小公约数方法
Math.gcd = function(a,b){
var min = Math.min(a,b);
var max = Math.max(a,b);
var result = 1;
if(a === 0 || b===0){
return max;
}
for(var i=min; i>=1; i--){
if(min % i === 0 && max % i === 0){
result = i;
break;
}
}
return result;
};

//使用clone元素对象拷贝仍然会造成浪费，但是使用权重数组对应关系更省内存
var weight_arr = new Array();
for (i = 0; i < arr.length; i++) {
if('undefined' != typeof(arr[i].weight))
{
if(arr[i].weight.toString().indexOf('%') !== -1) {
per = Math.floor(arr[i].weight.toString().replace('%',''));
perMode = true;
}else{
per = Math.floor(arr[i].weight100);
}
}else{
per = 0;
}
weight_arr[i] = per;
maxNum = Math.gcd(maxNum,per);
}
//数字比模式，3:5:7，其组成[0,1,2]
//百分比模式，元素所占百分比为15%，25%，35%
var index = new Array();
var total = 0;
var len = 0;
if(perMode){
for (i = 0; i < arr.length; i++) {
//len表示存储arr下标的数据块长度，已优化至最小整数形式减小索引数组的长度
len = weight_arr[i];
for (j = 0; j < len; j++){
//超过100%跳出，后面的舍弃
if(total >= 100){
break;
}
index.push(i);
total++;
}
}
//使用最后一个元素补齐100%
while(total < 100){
index.push(arr.length-1);
total++;
}
}else{
for (i = 0; i < arr.length; i++) {
//len表示存储arr下标的数据块长度，已优化至最小整数形式减小索引数组的长度
len = weight_arr[i]/maxNum;
for (j = 0; j < len; j++){
index.push(i);
}
total += len;
}
}
//随机数值，其值为0-11的整数，数据块根据权重分块
var rand = Math.floor(Math.random()total);
//console.log(index);
return arr[index[rand]];
}

var arr=[{name:'1',weight:3.5}];
console.log(weight_rand(arr));
var arr=[{name:'1',weight:'35%'}];
console.log(weight_rand(arr));
var prize_arr = [
{'id':1,'prize':'平板电脑','weight':1},{'id':2,'prize':'数码相机','weight':2},{'id':3,'prize':'音箱设备','weight':10},{'id':4,'prize':'4G优盘','weight':12},{'id':5,'prize':'10Q币','weight':22},{'id':6,'prize':'下次没准就能中哦','weight':50}
];

var times = 100000;
var prize;
var pingban = 0;
var shuma = 0;
var yinxiang = 0;
var youpan = 0;
var qb = 0;
var xc = 0;
var start = new Date().getTime();

for($i=0; $i<times; $i++){
prize = weight_rand(prize_arr);
if(prize.prize == '平板电脑')
{
pingban++;
}else if(prize.prize == '数码相机'){
shuma++;
}else if(prize.prize == '音箱设备'){
yinxiang++;
}else if(prize.prize == '4G优盘'){
youpan++;
}else if(prize.prize == '10Q币'){
qb++;
}else if(prize.prize == '下次没准就能中哦'){
xc++;
}
}

var stop = new Date().getTime();
console.log('平板电脑：'+pingban/times+',数码相机：'+shuma/times+',音箱设备：'+yinxiang/times+',4G优盘：'+youpan/times+',10Q币：'+qb/times+',下次没准就能中哦：'+xc/times);
console.log('耗费时间：'+(stop-start)/1000+'秒');

'1','weight'=>1.5),array('name'=>'2',array('name'=>'3','weight'=>1.5)); //$arr=array(array('name'=>'1','weight'=>'15%'),'weight'=>'25%'),'weight'=>'35%')); //求出最大公约数以计算缩小倍数，perMode为百分比模式 $perMode = false; $maxNum = 0; //自定义求最小公约数方法 $gcd = function($a,$b) { $min = min($a,$b); $max = max($a,$b); $result = 1; if($a === 0 || $b === 0) { return $max; } for($i=$min; $i>=1; $i--) { if($min % $i === 0 && $max % $i === 0) { $result = $i; break; } } return $result; }; //使用传地址可能会影响后面的结果，但是使用权重数组对应关系更省内存 $weight_arr = array(); $arr_len = count($arr); for($i=0; $i<$arr_len; $i++) { if(isset($arr[$i]['weight'])) { if(strpos($arr[$i]['weight'],'%') !== false) { $per = floor(str_replace('%','',$arr[$i]['weight'])); $perMode = true; }else{ $per = floor($arr[$i]['weight']*100); } }else{ $per = 0; } $weight_arr[$i] = $per; $maxNum = call_user_func($gcd,$maxNum,$per); } //数字比模式，3:5:7，其组成[0,2] //百分比模式，元素所占百分比为15%，25%，35% $index = array(); $total = 0; if($perMode) { for($i=0; $i<$arr_len; $i++) { //$len表示存储$arr下标的数据块长度，已优化至最小整数形式减小索引数组的长度 $len = $weight_arr[$i]; for ($j = 0; $j < $len; $j++) { //超过100%跳出，后面的舍弃 if($total >= 100) { break; } $index[] = $i; $total++; } } //使用最后一个元素补齐100% while($total < 100) { $index[] = $arr_len-1; $total++; } }else{ for($i=0; $i<$arr_len; $i++) { //len表示存储arr下标的数据块长度，已优化至最小整数形式减小索引数组的长度 $len = $weight_arr[$i]/$maxNum; for ($j = 0; $j < $len; $j++) { $index[] = $i; } $total += $len; } } //随机数值，其值为0-11的整数，数据块根据权重分块 $rand = floor(mt_rand(0,$total)); //修复php随机函数可以取临界值造成的bug $rand = $rand == $total ? $total-1 : $rand; return $arr[$index[$rand]]; }

$arr=array(array('name'=>'1','weight'=>1.5));
p(weight_rand($arr));
$arr=array(array('name'=>'1','weight'=>'35%'));
p(weight_rand($arr));

$prize_arr = array(
'0' => array('id'=>1,'prize'=>'平板电脑','weight'=>1),'1' => array('id'=>2,'prize'=>'数码相机','weight'=>5),'2' => array('id'=>3,'prize'=>'音箱设备','weight'=>10),'3' => array('id'=>4,'prize'=>'4G优盘','weight'=>12),'4' => array('id'=>5,'prize'=>'10Q币','weight'=>22),'5' => array('id'=>6,'prize'=>'下次没准就能中哦','weight'=>50),);

$start = time();
$result = array();
$times = 100000;
for($i=0; $i<$times; $i++)
{
$row = weight_rand($prize_arr);
if(array_key_exists($row['prize'],$result))
{
$result[$row['prize']] ++;
}else{
$result[$row['prize']] = 1;
}
}
$cost = time() - $start;

p($result);
p('耗费时间：'.$cost.'秒');
function p($var)
{
echo "

";

if($var === false)

{

echo 'false';

}else if($var === ''){

print_r("''");

}else{

print_r($var);

}

echo "

";
}