const sgMail = require('@sendgrid/mail');
sgMail.setApiKey(process.env.SENDGRID_API_KEY);
const msg = {
  to: 'test@example.com',
  from: 'test@example.com',
  subject: 'Sending with Twilio SendGrid is Fun',
  text: 'and easy to do anywhere, even with Node.js',
  html: '<strong>and easy to do anywhere, even with Node.js</strong>',
};
sgMail.send(msg);

以上使用需要导入sendgrid。上面的代码工作。
但是由于我使用的是ES6语法，所以我不能使用require，而必须使用import。

import sgMail from '@sendgrid/mail');
sgMail.setApiKey(process.env.SENDGRID_API_KEY);
const msg = {
  to: 'test@example.com',
  from: 'test@example.com',
  subject: 'Sending with Twilio SendGrid is Fun',
  text: 'and easy to do anywhere, even with Node.js',
  html: '<strong>and easy to do anywhere, even with Node.js</strong>',
};
sgMail.send(msg);

所以，我写了这段代码，但它给出了错误，因为变量未定义（阅读setApiKey）。当我把那条线拿掉。它给出错误，因为变量未定义（阅读发送）。