Student Activity

Student Activity (30-min)

Activity: Implement Middleware for Validation

Step-by-Step Procedure:

1. Step 1: Set Up the Project:

   • Initialize the project and install dependencies:

     bash코드 복사mkdir middleware-api
     cd middleware-api
     npm init -y
     npm install express express-validator

2. Step 2: Create app.js and Set Up Middleware:

   • Add a custom middleware for logging:

     javascript코드 복사const express = require('express');
     const { check, validationResult } = require('express-validator');
     const app = express();
     
     app.use(express.json());
     
     app.use((req, res, next) => {
         const time = new Date().toISOString();
         console.log(`[${time}] ${req.method} ${req.url}`);
         next();
     });
     
     const PORT = 3000;
     app.listen(PORT, () => console.log(`Server running on http://localhost:${PORT}`));

3. Step 3: Add Validation Middleware:

   • Add a POST route for validating tasks:

     javascript코드 복사app.post('/tasks', [
         check('title').isString().notEmpty(),
         check('completed').isBoolean()
     ], (req, res) => {
         const errors = validationResult(req);
         if (!errors.isEmpty()) {
             return res.status(400).json({ errors: errors.array() });
         }
         res.send('Task is valid');
     });

4. Step 4: Test the Application Using Postman:

   • Send a POST request to /tasks with a valid payload:

     json코드 복사{ "title": "Task 1", "completed": true }

   • Send another POST request with an invalid payload:

     json코드 복사{ "title": "", "completed": "yes" }

   • Observe the validation errors in the response.