使用ES6 import引入SendGrid Mail时出现变量未定义问题

问题场景 #

使用require引入SendGrid的代码可正常运行：

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);

改用ES6的import语法后，运行报错sgMail变量未定义，调用setApiKey和send时均提示变量不存在：

import sgMail from '@sendgrid/mail'); // 此处存在语法错误
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);

解决步骤 #

1. 修正语法错误
   原import语句末尾多了一个多余的右括号，正确写法为：

   import sgMail from '@sendgrid/mail';
   

2. 确保项目支持ES模块
   在项目根目录的package.json中添加"type": "module"字段，让Node.js将.js文件识别为ES模块：

   {
     "type": "module"
   }
   

   若不想修改package.json，可将文件后缀改为.mjs。

3. 调整导入方式（若上述步骤无效）
   部分版本的@sendgrid/mail可能使用命名导出而非默认导出，此时需改用整体导入：

   import * as sgMail from '@sendgrid/mail';
   

修正后的完整代码 #

import * as 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);

内容的提问来源于stack exchange，提问作者Manas telavane