JS抽奖算法的一种实现

let buffer = [0,1,2,3,4]; // 奖池

let buff_probability = [0.2, 0.2, 0.2, 0.2, 0.2]; // 概率

randomProbability(buffer, buff_probability )

function randomProbability(arr1, arr2) {
      var sum = 0,
      factor = 0,
      random = Math.random();
      for(var i = arr2.length - 1; i >= 0; i--) {
        sum += arr2[i]; // 统计概率总和
      };
      random *= sum; // 生成概率随机数
      for(var i = arr2.length - 1; i >= 0; i--) {
        factor += arr2[i];
        if(random <= factor) return arr1[i];
      };
      return null;
}