起步案例

路由设计

案例：通过该案例创建一个简单的 CRUD 接口服务，从而掌握 Express 的基础用法。

需求：实现对任务清单的 CRUD 接口服务。

• 查询任务列表：GET /todos
• 根据 ID 查询单个任务：GET /todos/:id
• 添加任务：POST /todos
• 修改任务：PATCH /todos
• 删除任务：DELETE /todos/:id

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

app.get('/todos', (req, res) => {
  res.send('get /todos');
});

app.get('/todos/:id', (req, res) => {
  res.send('get /todos/:id');
});

app.post('/todos', function (req, res) {
  res.send('post /todos');
});

app.patch('/todos/:id', function (req, res) {
  res.send('patch /todos/:id');
});

app.delete('/todos/:id', function (req, res) {
  res.send('delete /todos/:id');
});

app.listen(port, () => {
  console.log(`Example app listening at http://localhost:${port}`);
});

获取任务列表

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

app.get('/todos', (req, res) => {
  fs.readFile('./db.json', 'utf8', (err, data) => {
    if (err) {
      return res.status(500).json({
        err: err.message
      });
    }
    const db = JSON.parse(data);
    res.status(200).json(db.todos);
  });
});

app.listen(port, () => {
  console.log(`Example app listening at http://localhost:${port}`);
});

根据 ID 获取单个任务

app.get('/todos/:id', (req, res) => {
  fs.readFile('./db.json', 'utf8', (err, data) => {
    if (err) {
      return res.status(500).json({
        err: err.message
      });
    }
    const db = JSON.parse(data);
    const todo = db.todos.find(todo => todo.id === Number(req.params.id));
    if (!todo) {
      return res.status(404).end();
    }
    res.status(200).json(todo);
  });
});

封装 db 模块

// db.js
const fs = require('fs');
const path = require('path');
const { promisify } = require('util');
const readFile = promisify(fs.readFile);
const dbPath = path.join(__dirname, './db.json');

exports.getDb = async () => {
  const data = await readFile(dbPath, 'utf8');
  return JSON.parse(data);
};

假数据：

{
  "todos": [
    {
      "id": 1,
      "title": "吃饭"
    },
    {
      "id": 2,
      "title": "睡觉"
    },
    {
      "id": 3,
      "title": "写代码"
    },
    {
      "id": 4,
      "title": "看视频"
    }
  ],
  "users": []
}

// app.js
const express = require('express');
const { getDb } = require('./db');

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

app.get('/todos', async (req, res) => {
  try {
    const db = await getDb();
    res.status(200).json(db.todos);
  } catch (err) {
    res.status(500).json({
      err: err.message
    });
  }
});

app.get('/todos/:id', async (req, res) => {
  try {
    const db = await getDb();
    const todo = db.todos.find(todo => todo.id === Number(req.params.id));
    if (!todo) {
      return res.status(404).end();
    }
    res.status(200).json(todo);
  } catch (err) {
    res.status(500).json({
      err: err.message
    });
  }
});

app.listen(port, () => {
  console.log(`Example app listening at http://localhost:${port}`);
});

添加任务

app.post('/todos', async (req, res) => {
  try {
    const todo = req.body;
    if (!todo.title) {
      return res.status(422).json({
        err: 'The field title is required!'
      });
    }
    const db = await getDb();
    const lastTodo = db.todos[db.todos.length - 1];
    todo.id = lastTodo ? lastTodo.id + 1 : 1;
    db.todos.push(todo);
    await saveDb(db);
    res.status(201).json(todo);
  } catch (err) {
    res.status(500).json({
      err: err.message
    });
  }
});

修改任务

app.patch('/todos/:id', async (req, res) => {
  try {
    const todo = req.body;
    const db = await getDb();
    const ret = db.todos.find(todo => todo.id === Number(req.params.id));
    if (!ret) {
      return res.status(404).end();
    }
    Object.assign(ret, todo);
    await saveDb(db);
    res.status(200).json(ret);
  } catch (err) {
    res.status(500).json({
      err: err.message
    });
  }
});

删除任务

app.delete('/todos/:id', async (req, res) => {
  try {
    const todoId = Number(req.params.id);
    const db = await getDb();
    const index = db.todos.findIndex(todo => todo.id === todoId);
    if (index === -1) {
      return res.status(404).end();
    }
    db.todos.splice(index, 1);
    await saveDb(db);
    res.status(204).end();
  } catch (err) {
    res.status(500).json({
      err: err.message
    });
  }
});