Create Your API

APIs (Application Programming Interfaces) are the backbone of modern software development, enabling applications to communicate and share data efficiently. Whether you're building a project or looking to level up your development skills, creating your API is a fundamental milestone.

In this blog, we'll explore how to create a simple RESTful API from scratch using Node.js and Express.js, two popular tools for backend development.

Step 1: Initialize Your Project

1. Create a new project folder and navigate into it:

    mkdir my-api
    cd my-api
   

2. Initialize a new Node.js project:

    npm init -y
   

   This creates a package.json file to manage your project dependencies.

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Step 2: Install Dependencies

We'll use Express for building the API and nodemon for easier development.

npm install express
npm install --save-dev nodemon

Update the package.json file to use nodemon for running the project. Add this to the scripts section:

"scripts": {
  "start": "nodemon index.js"
}

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Step 3: Set Up the Basic API Structure

1. Create a file named index.js:

    touch index.js
   

2. Add the following code to index.js to set up a basic Express server:

    const express = require("express");
    const app = express();
   
    app.use(express.json()); // For parsing JSON requests
   
    const PORT = 3000;
   
    app.listen(PORT, () => {
        console.log(`Server is running on http://localhost:${PORT}`);
    });
   

Run your server:

npm start

Visit http://localhost:3000 in your browser or a tool like Postman to verify that the server is running.

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Step 4: Create Your First API Endpoint

Let’s create a simple GET endpoint:

1. Modify index.js to include the following route:

    app.get("/", (req, res) => {
        res.send("Welcome to My API!");
    });
   

2. Restart the server (nodemon should auto-restart if running). Open http://localhost:3000 in your browser, and you should see the message "Welcome to My API!".

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Step 5: Build a CRUD API

To demonstrate API capabilities, let’s build a CRUD (Create, Read, Update, Delete) API for managing "users."

1. Create an in-memory data store (array):

    const users = [
        { id: 1, name: "Alice" },
        { id: 2, name: "Bob" },
    ];
   

2. Add routes for each CRUD operation:

    // Get all users
    app.get("/users", (req, res) => {
        res.json(users);
    });
   
    // Get a user by ID
    app.get("/users/:id", (req, res) => {
        const user = users.find(u => u.id === parseInt(req.params.id));
        if (!user) return res.status(404).send("User not found.");
        res.json(user);
    });
   
    // Add a new user
    app.post("/users", (req, res) => {
        const user = { id: users.length + 1, name: req.body.name };
        users.push(user);
        res.status(201).json(user);
    });
   
    // Update a user
    app.put("/users/:id", (req, res) => {
        const user = users.find(u => u.id === parseInt(req.params.id));
        if (!user) return res.status(404).send("User not found.");
        user.name = req.body.name;
        res.json(user);
    });
   
    // Delete a user
    app.delete("/users/:id", (req, res) => {
        const index = users.findIndex(u => u.id === parseInt(req.params.id));
        if (index === -1) return res.status(404).send("User not found.");
        const deletedUser = users.splice(index, 1);
        res.json(deletedUser);
    });
   

3. Test the API using Postman or a similar tool. Try the following requests:

   • GET /users to fetch all users.

   • GET /users/:id to fetch a specific user.

   • POST /users with a JSON body like {"name": "Charlie"} to add a user.

   • PUT /users/:id with a JSON body like {"name": "David"} to update a user.

   • DELETE /users/:id to delete a user.

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Step 6: Error Handling and Validation

Improve the API by adding error handling and input validation:

1. Install the joi library:

    npm install joi
   

2. Update the POST and PUT routes to validate input:

    const Joi = require("joi");
   
    const validateUser = (user) => {
        const schema = Joi.object({
            name: Joi.string().min(3).required(),
        });
        return schema.validate(user);
    };
   
    app.post("/users", (req, res) => {
        const { error } = validateUser(req.body);
        if (error) return res.status(400).send(error.details[0].message);
   
        const user = { id: users.length + 1, name: req.body.name };
        users.push(user);
        res.status(201).json(user);
    });
   
    app.put("/users/:id", (req, res) => {
        const user = users.find(u => u.id === parseInt(req.params.id));
        if (!user) return res.status(404).send("User not found.");
   
        const { error } = validateUser(req.body);
        if (error) return res.status(400).send(error.details[0].message);
   
        user.name = req.body.name;
        res.json(user);
    });
   

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Step 7: Deploy Your API

Once your API is ready, deploy it to a platform like Render, Vercel, or Heroku.

1. Push your code to a GitHub repository.

2. Follow the deployment instructions for your chosen platform.

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You’ve built and deployed a fully functional RESTful API. This API can now serve as the backend for your web or mobile applications!

Happy coding 🚀

Do you have questions or feedback? Drop a comment below, or connect with me on LinkedIn and GitHub