如何实现随机步长递增的for循环，为location分配随机数量的boulder数据

核心需求 #

• 给每条location数据分配随机数量的boulder数据
• 需要实现按随机步长递增的for循环：初始索引为0，生成随机步长后索引叠加该步长进入下一轮迭代，例如首次生成随机数5则下一个索引为0+5，第二次生成随机数3则第三个索引为5+3，以此类推

现有代码片段 #

随机数生成函数 #

const randomNum = (min, max) => {
    min = Math.ceil(min);
    max = Math.floor(max);
    return Math.floor(Math.random() * (max - min) + min)
}

报错的原实现代码 #

const allBoulders = async() => {await Boulder.find().exec()}

for (i=0, i < allBoulders.length; i+=upperCount;) {
    console.log(i)
    const area = location.area;
    const place = location.place;
    const latitude = location.latitude;
    const longitude = location.longitude;
    const boulderLocation = new Location({area: area, place: place, latitude: latitude, longitude: longitude});
    const upperCount = indexCount + randomNum(1, 5)
    const boulderSet = allBoulders.slice(indexCount, upperCount);
    boulderLocation.boulders.push(...boulderSet);
    // await boulderLocation.save()
    console.log(boulderLocation)
    indexCount = upperCount;
};

报错信息 #

for (i=0, i < allBoulders.length; i+=upperCount;) {
                                     ^

ReferenceError: upperCount is not defined

已验证解决方案 #

修复后可运行代码 #

locations.forEach(async(location) => {
    const allBoulders =  await Boulder.find().exec()
    // console.log(foundAllBoulders);
    for (let i = 0; i < allBoulders.length;) {
        const area = location.area;
        const place = location.place;
        const latitude = location.latitude;
        const longitude = location.longitude;
        const boulderLocation = new Location({area: area, place: place, latitude: latitude, longitude: longitude});
        const random = randomNum(1, 5);
        const upperCount = i + random;
        const boulderSet = allBoulders.slice(i, upperCount);
        boulderLocation.boulders.push(...boulderSet);
        // await boulderLocation.save()
        console.log(boulderLocation);
        i += random;
    }
})

解决思路 #

原报错核心原因是upperCount变量在for循环的迭代器位置被调用时还未完成声明，同时原代码还存在异步函数调用错误、索引变量混用的问题。修复方案采用forEach遍历所有location数据，内部嵌套for循环，在循环体内优先生成随机步长，使用同一个随机值计算切片上限和索引增量，彻底避免变量提前引用问题。

内容的提问来源于stack exchange，提问作者shoski