在Array.map函数中使用await

Question

在遍历数组之前，我需要等待异步函数完成，需要等待解决的异步函数如下：

 static async sendEmail (from, to, subject, text) { return new Promise((resolve, reject) => { let message = { from, to, subject, text }; AMMailing.transporter.sendMail(message, function (err, response) { if (err) { reject(err); } else { resolve(response); } }); }); } 

这是我在数组中进行迭代并尝试等待其解决之后再进行迭代的方式的代码：

 static sendEmailInQueue (queue) { queue.map(async (person, index) => { console.log('sending email to: ', person.email); try { let success = await AMMailing.sendEmail(AMMailing.message.from, person.email, AMMailing.message.subject, AMMailing.message.text); if (success) { console.log('email sent to: ', person.email); } } catch (err) { console.log(err); } }); } 

我的问题是：这行console.log('sending email to: ', person.email); 一直执行，然后AMMailing.sendEmail（）函数开始记录其结果

这是我在控制台中得到的输出：

sending email to:  matheus.rezende10@gmail.com
sending email to:  matheus.rezende10@gmail.com
sending email to:  matheus.rezende10@gmail.com
sending email to:  matheus.rezende10@gmail.com
sending email to:  matheus.rezende10@gmail.com
sending email to:  matheus.rezende10@gmail.com
sending email to:  matheus.rezende10@gmail.com
sending email to:  matheus.rezende10@gmail.com
sending email to:  matheus.rezende10@gmail.com
sending email to:  matheus.rezende10@gmail.com
sending email to:  matheus.rezende10@gmail.com
{ Error: Hostname/IP doesn't match certificate's altnames: "Host: mail.appmasters.io. is not in the cert's altnames: DNS:*.sgcpanel.com, DNS:sgcpanel.com"

Answer 1

您无需在示例中使用map ，它没有映射任何内容。 您可以简单地使用for循环遍历数组，以按顺序等待每个项目。 例如：

static async sendEmailInQueue (queue) { // async method
  for (let i = 0; i < queue.length; i++) {
    try {
      // await sequentially
      let success = await AMMailing.sendEmail(/* ... */);
      if (success) {
        console.log('email sent to: ', person.email);
      }
    } catch (err) {
      console.log(err);
    }
  }
}

Answer 2

您可以随时使用.reduce()用的初始值Promise.resove()和顺序您promisified异步任务。

假设我们的异步sendMail(msg,cb)函数在0-250ms内发送邮件。 我们可以promisify它在我们的（如果它不返回一个承诺） sendMessages功能和顺序的承诺了.then()阶段中.reduce()

 function sendMail(msg, cb){ setTimeout(cb, Math.random()*250, false, "message to: " + msg.to + " is sent"); } function sendMessages(ms){ function promisify(fun, ...args){ return new Promise((v,x) => fun(...args, (err,data) => !!err ? x(err) : v(data))); } ms.reduce((p,m) => p.then(v => promisify(sendMail,m)) .then(v => console.log(v)), Promise.resolve()); } var msgArray = [{from: "x", to: "John@yyz.com", subject: "", text:""}, {from: "y", to: "Rose@ist.com", subject: "", text:""}, {from: "z", to: "Mary@saw.com", subject: "", text:""} ]; sendMessages(msgArray);