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js实现一个权重抽奖

2026-01-31 09:43:09JavaScript

权重抽奖实现方法

权重抽奖是一种根据每个奖项的权重值来随机抽取奖项的方法，权重越高，被抽中的概率越大。以下是使用JavaScript实现权重抽奖的几种方法。

方法一：基于数组的权重抽奖

定义一个奖项数组，每个奖项包含名称和权重。通过计算总权重，生成随机数，然后遍历数组确定中奖奖项。

js实现一个权重抽奖

function weightedDraw(prizes) {
    let totalWeight = prizes.reduce((sum, prize) => sum + prize.weight, 0);
    let random = Math.random() * totalWeight;
    let currentWeight = 0;

    for (let prize of prizes) {
        currentWeight += prize.weight;
        if (random <= currentWeight) {
            return prize.name;
        }
    }
}

// 示例
const prizes = [
    { name: "一等奖", weight: 1 },
    { name: "二等奖", weight: 3 },
    { name: "三等奖", weight: 6 },
    { name: "谢谢参与", weight: 90 }
];

console.log(weightedDraw(prizes));

方法二：使用概率分布

将权重转换为概率分布，然后使用累积概率进行抽奖。这种方法适用于权重较大的情况。

js实现一个权重抽奖

function weightedDrawWithProbability(prizes) {
    const totalWeight = prizes.reduce((sum, prize) => sum + prize.weight, 0);
    const probabilities = prizes.map(prize => prize.weight / totalWeight);
    const cumulativeProbabilities = [];
    let sum = 0;

    for (let prob of probabilities) {
        sum += prob;
        cumulativeProbabilities.push(sum);
    }

    const random = Math.random();
    for (let i = 0; i < cumulativeProbabilities.length; i++) {
        if (random <= cumulativeProbabilities[i]) {
            return prizes[i].name;
        }
    }
}

// 示例
const prizes = [
    { name: "一等奖", weight: 1 },
    { name: "二等奖", weight: 3 },
    { name: "三等奖", weight: 6 },
    { name: "谢谢参与", weight: 90 }
];

console.log(weightedDrawWithProbability(prizes));

方法三：使用二分查找优化

当奖项数量较多时，可以使用二分查找来提高效率。首先计算累积权重数组，然后使用二分查找确定中奖奖项。

function weightedDrawWithBinarySearch(prizes) {
    const totalWeight = prizes.reduce((sum, prize) => sum + prize.weight, 0);
    const cumulativeWeights = [];
    let sum = 0;

    for (let prize of prizes) {
        sum += prize.weight;
        cumulativeWeights.push(sum);
    }

    const random = Math.random() * totalWeight;
    let left = 0;
    let right = cumulativeWeights.length - 1;

    while (left < right) {
        const mid = Math.floor((left + right) / 2);
        if (random <= cumulativeWeights[mid]) {
            right = mid;
        } else {
            left = mid + 1;
        }
    }

    return prizes[left].name;
}

// 示例
const prizes = [
    { name: "一等奖", weight: 1 },
    { name: "二等奖", weight: 3 },
    { name: "三等奖", weight: 6 },
    { name: "谢谢参与", weight: 90 }
];

console.log(weightedDrawWithBinarySearch(prizes));

方法四：使用ES6的Map和reduce

利用ES6的Map和reduce方法简化代码，适用于现代JavaScript环境。

function weightedDrawWithMap(prizes) {
    const totalWeight = prizes.reduce((sum, prize) => sum + prize.weight, 0);
    const random = Math.random() * totalWeight;
    let currentWeight = 0;

    return prizes.find(prize => {
        currentWeight += prize.weight;
        return random <= currentWeight;
    }).name;
}

// 示例
const prizes = [
    { name: "一等奖", weight: 1 },
    { name: "二等奖", weight: 3 },
    { name: "三等奖", weight: 6 },
    { name: "谢谢参与", weight: 90 }
];

console.log(weightedDrawWithMap(prizes));