等待 aws lambda 函数中的 forEach 循环答案

【问题标题】：Waiting for forEach loop in aws lambda function等待 aws lambda 函数中的 forEach 循环
【发布时间】：2019-05-19 11:51:24
【问题描述】：

如何在 aws lambda 中执行 return 语句之前等待 forEach 循环完成？

module.exports.shipments = async (event) => {
    const axios = require("axios");
    let data = JSON.parse(event.body);
    let url = data.apiURL + "/api/1.1/wf/bulkshipments/initialize";
    let patchURL = data.apiURL + "/api/1.1/obj/company/" + data.companyID;

    data.shipments.forEach((item, index, array) => {
        axios.post(url,{
        batchID: data.batchID,
        companyID: data.companyID,
        shipment: item})
    });

    return {
      statusCode: 200,
      body: JSON.stringify({
        message: 'Created successfully!',
        totalShipments: data.shipments.length,
      }, null, 2),
    };
};

【问题讨论】：

标签： javascript node.js lambda async-await

【解决方案1】：

你已经在使用异步了，所以使用 map 返回一个 Promise 列表，并使用 Promise.all() 等待它们：

module.exports.shipments = async (event) => {
    const axios = require("axios");
    let data = JSON.parse(event.body);
    let url = data.apiURL + "/api/1.1/wf/bulkshipments/initialize";
    let patchURL = data.apiURL + "/api/1.1/obj/company/" + data.companyID;

    let promises = data.shipments.map(item =>
        axios.post(url, {
            batchID: data.batchID,
            companyID: data.companyID,
            shipment: item})
        })
    );

    await Promise.all(promises);

    return {
      statusCode: 200,
      body: JSON.stringify({
        message: 'Created successfully!',
        totalShipments: data.shipments.length,
      }, null, 2),
    };
};

要让每个呼叫等待，而不是同时触发所有发布请求，请使用for...of loop：

module.exports.shipments = async (event) => {
    const axios = require("axios");
    let data = JSON.parse(event.body);
    let url = data.apiURL + "/api/1.1/wf/bulkshipments/initialize";
    let patchURL = data.apiURL + "/api/1.1/obj/company/" + data.companyID;

    for (let item of data.shipments) {
        await axios.post(url, {
            batchID: data.batchID,
            companyID: data.companyID,
            shipment: item})
        });
    }

    await Promise.all(promises);

    return {
      statusCode: 200,
      body: JSON.stringify({
        message: 'Created successfully!',
        totalShipments: data.shipments.length,
      }, null, 2),
    };
};

【讨论】：

如何在每次通话之间添加延迟？