---
lang: ja-jp
breaks: true
---
# Node.js express を使用したWebアプリ Hello World　2021-05-10

> Node.js と Express を使用して Web API を構築する
> https://docs.microsoft.com/ja-jp/learn/modules/build-web-api-nodejs-express/

## Node.js プロジェクト作成

$ npm init -y
$ npm install express

$ touch app.js 

## app.js

const express = require('express');
const app = express();
const port = 3000;

var content_type = {
    'Content-Type': 'text/plain; charset=utf-8'
};

app.get('/', (req, res) => {
        res.header.apply(content_type);
        res.send('こんにちは　世界！！');
    }
);

// JSON データを返す
app.get("/products", (req, res) => {
        const products = [
            {
                id   : 1,
                name : "hammer",
            },
            {
                id   : 2,
                name : "screwdriver",
            },

            {
                id   : 3,
                name : "wrench",
            },
        ];
        res.json(products);
    }
);

app.get("/products/:id", (req, res) => {
        res.header.apply(content_type);
        res.send('products id:' + req.params.id);
    }
);

app.listen(port, () => { 
        console.log(`Example app listening on port ${port}!`);
    }
);

## package.json

{
  "name": "express_sample",
  "version": "1.0.0",
  "description": "",
  "main": "app.js",
  "scripts": {
    "start" : "node app.js",
    "test": "echo \"Error: no test specified\" && exit 1",
  },
  "repository": {
    "type": "git",
    "url": "git+https://github.com/xxxx/express_sample.git"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "bugs": {
    "url": "https://github.com/xxxx/express_sample/issues"
  },
  "homepage": "https://github.com/xxxx/express_sample#readme",
  "dependencies": {
    "express": "^4.17.1"
  }
}

## 実行

$ npm start

> express_sample@1.0.0 start /home/xxxx/work/nodejs/express_sample
> node app.js

Example app listening on port 3000!

###### tags: `Node.js` `express` `Hello World`