Node.js导出Map对象后导入出现TypeError/undefined问题

相关文件代码 #

launches.model.js #

const launches = new Map();
const launch = {
  flightNumber: 100,
  mission: "Kepler Exploration X",
  rocket: "Explorer IS1",
  launchDate: new Date("December 27,2030"),
  destination: "Kepler-442 b",
  customer: ["ZTM", "NASA"],
  upcoming: true,
  success: true,
};
launches.set(launch.flightNumber, launch);
console.log(launches);
module.export = {
  launches,
};   

该文件执行时console.log输出：

[Map Iterator] {
  {
    flightNumber: 100,
    mission: 'Kepler Exploration X',
    rocket: 'Explorer IS1',
    launchDate: 2030-12-26T18:30:00.000Z,
    destination: 'Kepler-442 b',
    customer: [ 'ZTM', 'NASA' ],
    upcoming: true,
    success: true
  }
}

launches.controller.js #

const { launches } = require("../../models/launches.model");
console.log(launches.values());

该文件执行时console.log报错：

c:\Users\kulji\Box\PROJECTS\NODE\NASA-PROJECT\server\src\routes\launches\launches.controller.js:3
console.log(launches.values());
                     ^
 
TypeError: Cannot read properties of undefined (reading 'values')

问题原因及修复 #

问题出在launches.model.js的导出语句上——你写了module.export，但Node.js中正确的导出语法是module.exports（注意末尾的s）。

修改launches.model.js的最后一段代码：

// 原错误代码
module.export = {
  launches,
};   

// 修改后正确代码
module.exports = {
  launches,
};   

修改后，launches.controller.js就能正确导入launches Map对象，调用values()方法也不会再报错。

内容的提问来源于stack exchange，提问作者kuljit-dhanoa