Question

我有3条记录。为了更新每条记录，我需要获取上一条记录的值。问题是方法是异步记录时，记录三在记录二完成之前开始更新并获取null值。我该如何处理？

const resolvePersons = async (persons) => {
      return Promise.all(persons.map(async (person) => {
        const data = await getSomePersonData(person);
        const value = await getValue(persons); // first person value is statically set
        return { data, value };
      }));
};

function getSomePersonData(person) {
    return new Promise((resolve, reject) => setTimeout(() => resolve({data: someData}), 100);
}

function getValue(persons) {
    return new Promise((resolve, reject) => setTimeout(() => resolve(persons[index - 1].value), 100);
}

Answer 1

如果您不希望迭代同时运行，请不要使用Promise.all和map。只需编写一个await有问题的普通循环即可：

async function resolvePersons(persons) {
    const result = [];
    for (const [i, person] of persons.entries()) {
        const data = await getSomePersonData(person);
        const prevValue = i == 0 ? null : result[i-1].value;
        const value = await getValue(prevValue);
        result.push({ data, value });
    }
    return result;
}

获取异步功能中的上一项

1 个答案: