[ TypeScript ] 環境構築でWebsocketServer.js:10エラーになる時 – ソフトウェアエンジニアの技術ブログ：Software engineer tech blog

### コンパイラ導入
$ node -v
v10.19.0
$ sudo npm install -g typescript
$ tsc -v
Version 4.4.3

hello.ts

const message:string = 'Hello! TypeScript!'
console.log(message);

$ tsc hello.ts
$ ls
hello.js hello.ts
$ node hello.js
Hello! TypeScript!

### npm環境
$ npm install typescript ts-loader webpack webpack-cli webpack-dev-server –save-dev

package.json

  // 省略
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "build": "webpack --mode=development",
    "start": "webpack-dev-server --mode=development"
  },
　　　　// 省略

webpack.config.js

const path = require('path');
module.exports = {
	entry: {
		bundle: './src/app.ts'
	},
	output: {
		path: path.join(__dirname,'dist'),
		filename: '[name].js'
	},
	resolve: {
		extensions:['.ts','.js']
	},
	devServer: {
		contentBase: path.join(__dirname,'dist')
	},
	module: {
		rules: [
			{
				test:/\.ts$/,loader:'ts-loader'
			}
		]
	}
}

$ tsc –init
-> tsconfig.json が生成される

dist, srcフォルダを作成する

src/app.ts

import {Item} from './item';
var elem = document.getElementById('output');
var aBook = new Item('はじめてのTypeScript', 2020);
aBook.say(elem);

src/item.ts

export class Item {
	constructor(private name:string, private price:number){}

	public say(elem: HTMLElement | null) : void {
		if(elem){
			elem.innerHTML = '書名:' + this.name + ' 価格: ' + this.price + '円';
		}
	}
}

dist/index.html

<body>
	<div id="output"></div>
	<script src="bundle.js"></script>
</body>
</html>

$ npm run start

> tutorial@1.0.0 start /home/vagrant/dev/typescript/tutorial
> webpack-dev-server –mode=development

[webpack-cli] /home/vagrant/dev/typescript/tutorial/node_modules/webpack-dev-server/lib/servers/WebsocketServer.js:10
static heartbeatInterval = 1000;

何でだろう？　なんかエラーになるな。。

$ sudo apt-get purge nodejs

▼この記事を参考に最新版を入れる
https://www.digitalocean.com/community/tutorials/how-to-install-node-js-on-ubuntu-20-04-ja

$ cd ~
$ curl -sL https://deb.nodesource.com/setup_14.x -o nodesource_setup.sh
$ sudo bash nodesource_setup.sh
$ sudo apt install nodejs
$ node -v
v14.17.6
$ npm run start

http://192.168.34.10:8000/

nodeがv10だとwebpack-dev-serverでエラーになるみたい　
https://github.com/VickScarlet/lifeRestart/issues/176
v14にupgradeするとエラー解消
マジかよ~~~~ もうやだー