_laravelEcho2.default不是构造函数

Question

我正在尝试使Laravel 5.4应用程序具有通知系统。我的package.json看起来像

{
  "private": true,
  "scripts": {
    "prod": "gulp --production",
    "dev": "gulp watch"
  },
  "devDependencies": {
    "bootstrap-sass": "^3.3.7",
    "gulp": "^3.9.1",
    "jquery": "^3.1.0",
    "laravel-elixir": "^6.0.0-9",
    "laravel-elixir-vue": "^0.1.4",
    "laravel-elixir-webpack-official": "^1.0.2",
    "lodash": "^4.14.0",
    "vue": "^1.0.26",
    "vue-resource": "^0.9.3"
  },
  "dependencies": {
    "laravel-echo": "^1.5.1",
    "laravel-echo-server": "^1.5.0",
    "pusher-js": "^4.3.1"
  }
}

但是，当我打开网页时，我在控制台中看到了附件错误。