使用 Nodemailer 时如何修复 "await is only valid in async function" 错误

How to fix "await is only valid in async function" error when using Nodemailer

我正在尝试按照教程使用 Nodemailer 创建联系我们表单。本教程从Nodemailer网站上粘贴了一些代码,但是自从录制该教程以来,源代码已更新。

我粘贴了网站上的最新代码,但出现以下控制台错误:

let info = await transporter.sendMail(mailOptions)

SyntaxError: await is only valid in async function

下面是我的 app.js 代码:

const express = require("express");
const bodyParser = require("body-parser");
const exphbs = require("express-handlebars");
const path = require("path");
const nodemailer = require("nodemailer");

const app = express();

// View engine setup
app.engine("handlebars", exphbs());
app.set("view engine", "handlebars");

// Static folder
app.use("/public", express.static(path.join(__dirname, "public")));

// Body Parser Middleware
app.use(bodyParser.urlencoded({ extended: false }));
app.use(bodyParser.json());

app.get("/", (req, res) => {
  res.render("contact");
});

app.post("/send", (req, res) => {
  const output = `
    <p>You have a new contact request</p>
    <h3>Contact Details</h3>
    <ul>
        <li>Name: ${req.body.name}</li>
        <li>Company: ${req.body.company}</li>
        <li>Email: ${req.body.email}</li>
        <li>Phone: ${req.body.phone}</li>
    </ul>
    <h3>Message</h3>
    <p>${req.body.message}</p>    
    `;
    
    var transporter = nodemailer.createTransport({
        service: 'gmail',
        auth: {
               user: 'youremail@address.com',
               pass: 'yourpassword'
           }
       });

       const mailOptions = {
        from: 'sender@email.com', // sender address
        to: 'to@email.com', // list of receivers
        subject: 'Subject of your email', // Subject line
        html: '<p>Your html here</p>'// plain text body
      };

      let info = await transporter.sendMail(mailOptions)

  console.log("Message sent: %s", info.messageId);
  console.log("Preview URL: %s", nodemailer.getTestMessageUrl(info));
  
});

app.listen(3000, () => console.log("Server started..."));

我粘贴的代码位于此页面:https://nodemailer.com/about/

为什么我会收到此错误,我需要进行哪些更改才能使代码按预期工作?

那是因为await只在async函数内部有效。语法是

async function some() {
  await other
}

更改此行:

app.post("/send", (req, res) => {

注意这里的async关键字 app.post("/send", async (req, res) => {

阅读更多关于 async/await

transporter.sendMail(mailOptions) 是异步操作,因此该示例在它之前使用 await 关键字以使执行同步。

但是,await 关键字只能在标记为 async 的方法中使用。因此,在您的情况下,您需要将 createTransport 方法标记为异步。

例如: async nodemail.createTransport 另一种选择是从方法中返回 transport.sendMail() 并解决承诺。

例如:

var transporter = nodemailer.createTransport({
        service: 'gmail',
        auth: {
               user: 'youremail@address.com',
               pass: 'yourpassword'
           }
       });

       const mailOptions = {
        from: 'sender@email.com', // sender address
        to: 'to@email.com', // list of receivers
        subject: 'Subject of your email', // Subject line
        html: '<p>Your html here</p>'// plain text body
      };

      return transporter.sendMail(mailOptions)

});

transport.then(
result =>   {
  console.log("Message sent: %s", result.info.messageId);
  console.log("Preview URL: %s", nodemailer.getTestMessageUrl(result.info));
}
);

如果不使函数异步,则不能使用 await。所以,只需将异步放在 (req, res) 之前,如下所示。

app.post("/send", async (req, res) => {
     //other stuff will goes here.
     let info = await transporter.sendMail(mailOptions)
});

await 只能在 async 函数中使用。

需要注意的是async函数仅用于使 promise 以更舒适的方式工作。

所以只需像这样添加 asyncapp.post("/send", async (req, res) => 或从

中删除 let info = await
`let info = await transporter.sendMail(mailOptions) 

而是像这样使用 then

transporter.sendMail(mailOptions).then((info) => { your code})