Javascript asyn/await 未按預期運行

Question

我目前正試圖掌握 javascript 上的異步/等待，但無法理解為什么 7 在一切結束時都沒有運行。 我知道罪魁禍首是調用 axios.get 命令導致延遲，但為什么我們不等待他們完成繼續前進？ 我認為任何 await 命令都會暫停事件循環，直到等待的函數返回某些內容。

結果：

0
1
before 2
1
before 2
7 - Writing to file ----------------------------------------------------------------------------------
(node:21116) UnhandledPromiseRejectionWarning: ReferenceError: result is not defined
    at processOrders (C:\Users\ReactFootwear\Desktop\Nodejs - Shopify Order System\app.js:30:5)
    at processTicksAndRejections (internal/process/task_queues.js:97:5)
(node:21116) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
(node:21116) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
2
3
2
3
4
5
6

我的代碼

const axios = require('axios').default;
const excel = require('exceljs');
const imageToBase64 = require('image-to-base64');
const fs = require('fs');


callShopifyOrdersApi();

// Get orders from shopify Api
async function callShopifyOrdersApi(){
  const url = 'https://shopifyurlhere.com/admin/api/2020-10/orders.json?created_at_min=2020-11-14'
  let responseData = await axios.get(url);
  processOrders(responseData.data.orders);

};


function processOrders(orders){
  console.log("Processing orders bitches");
  createWorkbook(orders).then(result => {

    console.log("7 - Writing to file ------------------------------------------------------------");

    var fileName = "Orders.xlsx";
    result.xlsx.writeFile(fileName).then(() => {
    });
  })
};


async function createWorkbook(orders){

    //Creating New Workbook 
    var workbook = new excel.Workbook();

    //Creating Sheet for that particular WorkBook
    var sheetName = 'Sheet1';
    var sheet = workbook.addWorksheet(sheetName);
    sheet.properties.defaultRowHeight = 200;

    //HEADER FORMAT
    sheet.columns = [ {key:"name", header:"name", width: 25}, {key: "address", header: "address"}];

    console.log("0")
    await compileRows(workbook, sheet, orders).then((workbook) => {return workbook})
  }


async function compileRows(workbook, sheet, orders){
  var rows = [];

  orders.forEach(async function (order) {

    order.line_items.forEach(async function (line_item, i) {
      var row = { name: order.customer.first_name , address: order.shipping_address.address1 }
      sheet.addRow(row);

    var img = await mainGetLineItemImg(line_item);
    
    console.log("3");

      if(i == 0){
 
        console.log("4");
        // add image to workbook by buffer
        const imageId2 = await workbook.addImage({
          buffer: fs.readFileSync('/Users/admin/Desktop/test.jpg'),
          extension: 'jpeg',
        });

        console.log("5");
        await sheet.addImage(imageId2, {
          tl: { col: 0, row: 3 },
          ext: { width: 180, height: 180 }
        });
        console.log("6");
      }
    });
  });
}


//GETTING IMAGE BASE 64
async function mainGetLineItemImg(line_item){
  console.log("1");
  var productId = line_item.product_id;
  var variantId = line_item.variant_id;
  console.log("before 2");

  const url = 'https://shopifyurlhere.com/admin/api/2020-10/variants/'+variantId+'.json';
  let responseData = await axios.get(url);
  var imageId = await responseData.data.variant.image_id;

  const url2 = 'https://shopifyurlhere.com/admin/api/2020-10/products/'+productId+'/images/'+imageId+'.json';
  let responseData2 = await axios.get(url2);
  var src = await responseData2.data.image.src;
  var base64code = await imageToBase64(src);


  console.log("2");
  return base64code;
}

Answer 1

看起來您的問題出在compileRows函數中。 您正在調用orders.forEach() ，它會立即運行，而無需等待其回調函數中發生的任何異步內容。 所以compileRows幾乎立即完成。

相反，使用for循環以便您可以實際await異步操作：

async function compileRows(workbook, sheet, orders){
  for (const order of orders) {
    for (let i = 0; i < order.line_items.length; i += 1) {
      const line_item = order.line_items[i];

      var row = { name: order.customer.first_name , address: order.shipping_address.address1 }
      sheet.addRow(row);

      var img = await mainGetLineItemImg(line_item);
    
      console.log("3");

      if(i == 0){
 
        console.log("4");
        // add image to workbook by buffer
        const imageId2 = await workbook.addImage({
          buffer: fs.readFileSync('/Users/admin/Desktop/test.jpg'),
          extension: 'jpeg',
        });

        console.log("5");
        await sheet.addImage(imageId2, {
          tl: { col: 0, row: 3 },
          ext: { width: 180, height: 180 }
        });
        console.log("6");
      }
    }
  }
}