Implement todo API

backend/controller/todo.js

@@ -0,0 +1,111 @@
+const TodoModel = require("../model/todo");
+const { validateCreate, validateUpdate } = require("../validation/todo");
+
+// function for collecting data then convert into json
+function parseBody(req) {
+  return new Promise((resolve, reject) => {
+    let raw = "";
+    req.on("data", (chunk) => (raw += chunk));
+    req.on("end", () => {
+      try { 
+        resolve(raw ? JSON.parse(raw) : {}); 
+        }
+      catch { 
+        reject({ 
+            status: 400, 
+            message: "Invalid JSON" 
+        }); 
+        }
+    });
+  });
+}
+// helper to send json responses back to client
+function send(res, status, data) {
+  const body = JSON.stringify(data);
+  res.writeHead(status, { 
+    "Content-Type": "application/json" 
+    });
+  res.end(body);
+}
+
+const TodoController = {
+// get all data
+  getAll(req, res) {
+    // response json
+    send(res, 200, { 
+        success: true, 
+        data: TodoModel.findAll() 
+    });
+  },
+// get single data
+  getOne(req, res, id) {
+    const todo = TodoModel.findById(id);
+    // if no todo then return
+    if (!todo) return send(res, 404, { 
+        success: false, 
+        error: `Todo ${id} not found` 
+    });
+    // successfull json
+    send(res, 200, { 
+        success: true, 
+        data: todo });
+  },
+// create a todo
+  async create(req, res) {
+    // get the parse json
+    const body = await parseBody(req);
+    // get the validation for create
+    const errors = validateCreate(body);
+
+    // check if has error
+    if (errors.length) return send(res, 400, { 
+        success: false, 
+        errors 
+    });
+
+    // if success then create
+    const todo = TodoModel.create(body);
+    send(res, 201, { 
+        success: true, 
+        data: todo 
+    });
+  },
+// update a todo
+  async update(req, res, id) {
+    const body = await parseBody(req);
+    const errors = validateUpdate(body);
+    // check if has any error
+    if (errors.length) return send(res, 400, { 
+        success: false, 
+        errors 
+    });
+    // if no id found
+    const todo = TodoModel.update(id, body);
+    if (!todo) return send(res, 404, { 
+        success: false, 
+        error: `Todo ${id} not found` 
+    });
+    // if success then update
+    send(res, 200, { 
+        success: true, 
+        data: todo 
+    });
+  },
+
+// delete a todo
+  delete(req, res, id) {
+    const deleted = TodoModel.delete(id);
+    // if no id found
+    if (!deleted) return send(res, 404, { 
+        success: false, 
+        error: `Todo ${id} not found` 
+    });
+    // if success then delete
+    send(res, 200, { 
+        success: true, 
+        message: `Todo ${id} deleted` 
+    });
+  },
+};
+// export to use 
+module.exports = TodoController;

backend/model/todo.js

@@ -0,0 +1,54 @@
+// local storage
+let todos = [
+  { 
+    id: 1, 
+    title: "Buy groceries", 
+    completed: false, 
+    createdAt: new Date().toISOString() 
+  },
+  { 
+    id: 2, 
+    title: "Read a book",   
+    completed: true,  
+    createdAt: new Date().toISOString() 
+  },
+];
+
+let nextId = 3;
+
+const TodoModel = {
+// get all data
+  findAll() {
+    return todos;
+  },
+// get by id
+  findById(id) {
+    return todos.find((t) => t.id === id) || null;
+  },
+// create a todo
+  create({ 
+    title, 
+    completed = false 
+    }) {
+    const todo = { id: nextId++, title: title.trim(), completed, createdAt: new Date().toISOString() };
+    todos.push(todo);
+    return todo;
+  },
+// update a todo
+  update(id, fields) {
+    const todo = todos.find((t) => t.id === id);
+    if (!todo) return null;
+    if (fields.title !== undefined) todo.title = fields.title.trim();
+    if (fields.completed !== undefined) todo.completed = fields.completed;
+    return todo;
+  },
+// delete a todo
+  delete(id) {
+    const index = todos.findIndex((t) => t.id === id);
+    if (index === -1) return false;
+    todos.splice(index, 1);
+    return true;
+  },
+};
+// export
+module.exports = TodoModel;

backend/package.json

@@ -2,9 +2,15 @@
   "name": "backend",
   "version": "1.0.0",
   "scripts": {
-    "start": "node index.js"
+    "start": "node server.js"
   },
   "dependencies": {
-    "express": "^4.18.2"
-  }
+    "express": "^4.22.1"
+  },
+  "description": "",
+  "main": "server.js",
+  "keywords": [],
+  "author": "",
+  "license": "ISC",
+  "type": "commonjs"
 }

backend/readme.md

@@ -0,0 +1,66 @@
+Api testing guide
+
+server: http://localhost:3000
+
+Endpoints:
+| Method    | Url           | Description           |
+| Get       | /api/todos    | Get all data          |
+| Get       | /api/todos/:id| Get single data ny id |
+| Post      | /api/todos    | Create a todo         |   // must have json data including title and completed
+| Put       | /api/todos/:id| Update a single todo  |    // must have json data either title or completed
+| Delete    | /api/todos/:id| Delete a todo         |
+
+Sample json success data:
+    - Fetching all data
+        {
+            "success": true,
+            "data": [
+                {
+                    "id": 1,
+                    "title": "Buy groceries",
+                    "completed": false,
+                    "createdAt": "2026-02-17T03:47:54.454Z"
+                },
+                {
+                    "id": 2,
+                    "title": "Read a book",
+                    "completed": true,
+                    "createdAt": "2026-02-17T03:47:54.454Z"
+                }
+            ]
+        }
+    - Get one Data
+        {
+            "success": true,
+            "data": {
+                "id": 1,
+                "title": "Buy groceries",
+                "completed": false,
+                "createdAt": "2026-02-17T03:47:54.454Z"
+            }
+        }
+    - Created todo
+        {
+            "success": true,
+            "data": {
+                "id": 3,
+                "title": "Create a new todo",
+                "completed": false,
+                "createdAt": "2026-02-17T05:05:56.386Z"
+            }
+        }
+    - Updated todo
+        {
+            "success": true,
+            "data": {
+                "id": 3,
+                "title": "Updated Title",
+                "completed": true,
+                "createdAt": "2026-02-17T05:05:56.386Z"
+            }
+        }
+    - Deleted todo
+        {
+            "success": true,
+            "message": "Todo 4 deleted"
+        }

backend/routes/todo.js

@@ -0,0 +1,28 @@
+const TodoController = require("../controller/todo");
+
+const TODO_LIST = /^\/api\/todos$/;
+const TODO_ITEM = /^\/api\/todos\/(\d+)$/;
+
+async function todoRouter(req, res) {
+  const method = req.method;
+  const url = req.url.split("?")[0];
+  const itemMatch = TODO_ITEM.exec(url);
+  const id = itemMatch ? parseInt(itemMatch[1]) : null;
+
+  // Collection: if url is equals to /api/todos
+  if (TODO_LIST.test(url)) {
+    if (method === "GET") return TodoController.getAll(req, res);
+    if (method === "POST") return TodoController.create(req, res);
+  }
+
+  // Item: if url is equals to /api/todos/:id
+  if (itemMatch) {
+    if (method === "GET") return TodoController.getOne(req, res, id);
+    if (method === "PUT") return TodoController.update(req, res, id);
+    if (method === "DELETE") return TodoController.delete(req, res, id);
+  }
+
+  return null; // no match
+}
+// exports
+module.exports = todoRouter;

backend/server.js

@@ -0,0 +1,39 @@
+const http = require("http");
+const todoRouter = require("./routes/todo");
+
+const PORT = process.env.PORT || 3000;
+
+const server = http.createServer(async (req, res) => {
+  try {
+    const handled = await todoRouter(req, res);
+    if (handled === null) {
+      res.writeHead(404, { 
+        "Content-Type": "application/json" 
+      });
+      res.end(JSON.stringify({ 
+        success: false, 
+        error: `Cannot ${req.method} ${req.url}` 
+      }));
+    }
+  } catch (err) {
+    console.error(err);
+    res.writeHead(500, { 
+      "Content-Type": "application/json" 
+    });
+    res.end(JSON.stringify({ 
+      success: false, 
+      error: "Internal server error" 
+    }));
+  }
+});
+
+server.listen(PORT, () => {
+  console.log(`Server running on http://localhost:${PORT}`);
+  console.log("GET    /api/todos");
+  console.log("GET    /api/todos/:id");
+  console.log("POST   /api/todos");
+  console.log("PUT    /api/todos/:id");
+  console.log("DELETE /api/todos/:id");
+});
+
+module.exports = server;

backend/validation/todo.js

@@ -0,0 +1,30 @@
+// validation for create
+function validateCreate(body) {
+  const errors = [];
+
+  if (!body.title || typeof body.title !== "string" || !body.title.trim()) {
+    errors.push("'title' is required and must be a non-empty string");
+  }
+  if (body.completed !== undefined && typeof body.completed !== "boolean") {
+    errors.push("'completed' must be a boolean");
+  }
+  return errors;
+}
+// validation for update
+function validateUpdate(body) {
+  const errors = [];
+
+  if (Object.keys(body).length === 0) {
+    errors.push("Body must include at least 'title' or 'completed'");
+  }
+  if (body.title !== undefined && (typeof body.title !== "string" || !body.title.trim())) {
+    errors.push("'title' must be a non-empty string");
+  }
+  if (body.completed !== undefined && typeof body.completed !== "boolean") {
+    errors.push("'completed' must be a boolean");
+  }
+
+  return errors;
+}
+// export
+module.exports = { validateCreate, validateUpdate };