Javascript async/await :文件读取时出现未定义错误

Question

我正在尝试使用 for 循环发送电子邮件async/await.

const prepareNotification =(genie)=>{
genie.forEach(async (item)=>{
if(item.is_active){
if(item.is_email){
sendEmailNotification(item);
}
}else{
console.log('deal genie inactive for',item.name);
}
});
}

对于发送，我需要从文件中读取 HTML 并发送到邮件功能。

const sendEmailNotification=async (item)=>{
try{
let emailTemplate = await fs.readFile(__basedir+'/controllers/html/sharedeal.html','utf-8');
console.log(emailTemplate);
let replacements = {
dealLink:'testlinkhere'
};
let mailOptions = {
from: process.env.smtpEmail,
to: item.email,
subject: 'DealLink',
replacements:replacements,
template:emailTemplate
};
let mail = await sendEmail(mailOptions);
}catch(error){
console.log(error);
}
}

但是我console.log(emailTemplate);得到了undefined，还有一个问题，如何确保sendEmailNotification在for循环中的每个状态上一个接一个地执行？

Answer 1

fs.readFile

不支持async/await。但是，您可以创建一个版本，该版本符合以下条件：

const util = require('util');
const readFileAsync = util.promisify(fs.readFile);

然后

let emailTemplate = await readFileAsync(__basedir+'/controllers/html/sharedeal.html','utf-8');
console.log(emailTemplate);

---

如何确保 sendEmailNotification 在 for 循环中的每个状态上一个接一个地执行？

const prepareNotification = async (genie) => {
for (let item of genie) {
if(item.is_active){
if(item.is_email){
await sendEmailNotification(item);
}
}else{
console.log('deal genie inactive for', item.name);
}
}
}

或

const prepareNotification = (genie) => {
genie.reduce((prev, item) => {
if(item.is_active){
if(item.is_email){
return prev.then(() => sendEmailNotification(item));
}
}else{
console.log('deal genie inactive for', item.name);
}
return prev;
}, Promise.resolve());
}