ES6 实例化失败，不知道问题出在哪里？

Question

track.js

class Track {
  constructor(title, artist, album, albumArt, audio) {
    this.title = title;
    this.artist = artist;
    this.album = album;
    this.albumArt = albumArt;
    this.audio = audio;
  };
  returnValue(){
    return(
      {
        title: this.title,
        artist: this.artist,
        album: this.album,
        audio: this.audio,
        albumArt: this.albumArt,
      }
    )
  }
}

search.js

import Track from '../models/track';

let a = new Track(1,2,3,4,5);

报错

error: Uncaught Exception. TypeError: _track2.default is not a constructor
    at Object.<anonymous> (/home/dev/Workspace/YuYin/build/main/features/search.js:13:9)
    at Object.<anonymous> (/home/dev/Workspace/YuYin/build/main/features/search.js:58:3)
    at Module._compile (module.js:571:32)
    at Object.Module._extensions..js (module.js:580:10)
    at Module.load (module.js:488:32)
    at tryModuleLoad (module.js:447:12)
    at Function.Module._load (module.js:439:3)
    at Module.require (module.js:498:17)
    at require (internal/module.js:20:19)
    at Object.<anonymous> (/home/dev/Workspace/YuYin/build/main/features/index.js:19:1)
    at Object.<anonymous> (/home/dev/Workspace/YuYin/build/main/features/index.js:22:3)
    at Module._compile (module.js:571:32)
    at Object.Module._extensions..js (module.js:580:10)
    at Module.load (module.js:488:32)
    at tryModuleLoad (module.js:447:12)
    at Function.Module._load (module.js:439:3)
    at Module.require (module.js:498:17)
    at require (internal/module.js:20:19)
    at App.<anonymous> (/home/dev/Workspace/YuYin/build/index.js:168:5)
    at emitTwo (events.js:111:20)
    at App.emit (events.js:191:7)

谁给看看， 不知道什么原因。。。

已经找到原因了， 忘记导出，在track.js最后加一行
export default Track;

Answer 1

export default class Track {...}

Answer 2

没有export这个class