Welcome to ZudoJS Academy

What the academy is

Open a banking app and tap "Transfer ₦5,000 to Tunde". Your phone does not move the money. It sends a message to another computer, far away, that says who you are, who Tunde is and how much to send. A program on that computer checks that it is really you, checks that you have ₦5,000, takes it from your account, adds it to Tunde's, writes both changes down so they are never lost, and answers "done". Your phone only shows the answer.

That program is the backend: the part of an application you do not see. The screen you tap is the front end. The same is true when a to-do app shows your tasks: the tasks are not stored on the phone. The app asks another computer for them, and a backend answers.

ZudoJS Academy is a free, hands-on school that teaches you to build backends, from your first line of code to a system running in production. It ends with ZudoJS, a framework (a set of ready-made, tested parts for building backends in TypeScript). ZudoJS is the destination, not the starting point: you first learn how each part of a backend works with no framework at all. Then, when you meet ZudoJS, you know exactly what each part does for you, and what to do when something goes wrong.

Who it is for

• Complete beginners. You have never written code. Every new word is explained the first time it appears.
• People who program in another language, such as Python, Java, PHP or C#, and want to build backends in JavaScript and TypeScript.
• JavaScript developers, including front-end developers, who want types and the server side.
• TypeScript backend developers who want to learn ZudoJS itself, and later how a framework is built.

You need a computer running Windows, macOS or Linux, where you can install programs. The first levels also work on a phone or tablet, in the browser. You do not need to be good at maths: the mathematics you need is taught in level 1.

Six tracks, 19 levels

The academy is one path of 19 levels. Each level is a course. A course is split into modules (groups of lessons on one subject), and each module into lessons. Level 4 has two courses side by side, so there are 20 courses in total. The levels are grouped into six tracks, and each track builds on the ones before it:

Together the courses hold hundreds of lessons, and new ones are added as they are written. The academy home shows every track and course, and the sidebar of each page shows where you are.

Here is your first program. Press Run in browser on it. A terminal opens at the bottom of the page and runs the code:

console.log("Hello! I am learning backend engineering.");
console.log("Tracks:", 6, "Levels:", 19);

Hello! I am learning backend engineering.
Tracks: 6 Levels: 19

The grey box under the example is its output: what the program printed. console.log prints one line each time it runs. When you give it several values separated by commas, it prints them on that line with one space between them. The quotes mark where a piece of text starts and ends; they are not printed.

Two more things you can already do with it. + between two pieces of text glues them into one, with nothing added in between. Numbers written without quotes are real numbers, so a sum is worked out before it is printed:

console.log("Task" + "API");
console.log("Task " + "API");
console.log("Levels after level 1:", 19 - 1);

TaskAPI
Task API
Levels after level 1: 18

The second line has a space inside the quotes of "Task ", so the joined text has one too. What programming is, later in this course, explains every part of a line like this. For now: it prints.

What you build

Every course page says what you build in that course. Across the academy, a few projects keep coming back, each bigger than the last:

A capstone is a final project that uses everything you have learned.

How a course page works

Each course has its own page, for example /learn/javascript. At the top, a breadcrumb line (Academy / track / course) shows where you are. Then the page shows:

• The level and track, and the course's tier (explained below).
• How long the course takes, and which course to finish before this one.
• A progress bar and a button that says Start lesson 1, or Continue where you left off once you have begun.
• When you finish, you can: the skills the course gives you, and You build: its project.
• The modules, each with its lessons in order.
• The course checkpoint: 20 questions picked at random from the tests of every lesson in the course. Get 16 right to pass. Pass it before you move to the next level.

Tiers

Every course, and sometimes a single lesson, carries one of four tier labels. The tier tells you how much you need it:

How a lesson page works

Every lesson page has the same shape. Its header says LEVEL n · LESSON i OF m: the level of the course, and where the lesson sits in it. Under that: the module, the time the lesson takes, what you need first and what you build. Then a box, By the end of this lesson you can, lists what the lesson teaches. Read it first, and check yourself against it at the end.

The lesson itself is short sections. Each one starts from a problem, shows a small example with its output, and explains that output. Three kinds of box ask you to do something:

• Reason it out: questions to think through before you see the code. What do you know? What can go wrong? What happens at the edges? Answer them yourself, then open Show the reasoning and compare.
• Try it yourself: an exercise. Solve it, then open Show a solution.
• Note, Tip and Warning boxes: short facts worth remembering.

Run in browser, and on your computer

You already met Run in browser. In the terminal you can change the code and run it again with Run or Ctrl + Enter. Nothing you type there can break anything. Try it: change the second line of the example below to print your own plan, and run it.

console.log("Level 1: Programming thinking");
console.log("Level 2: JavaScript fundamentals");
console.log("Goal:", "a backend in production");

Level 1: Programming thinking
Level 2: JavaScript fundamentals
Goal: a backend in production

The lines run from top to bottom, so the output comes in the same order as the code.

Some examples say Node.js only instead. They use things a browser is not allowed to do, like reading your files or starting a web server, so you run them on your own computer. The lesson then shows the exact commands in a box like this one:

$ node --version
v24.19.0

A line that starts with $ is a command for you to type. Do not type the $ itself. The lines under it are what the computer printed back (your version number may differ). You install Node.js in Set up your computer, so do not worry if this command does not work for you yet.

The editor

Every example has an Edit button, and every lesson has an Open the editor button at the top. The editor is a workspace that looks and works like Visual Studio Code: your files on the left, tabs at the top, and a terminal at the bottom. Change the code, press Run (Ctrl + Enter, or Cmd + Enter on a Mac), and the output appears in the terminal. You can create your own files, and files in the same folder can import each other, just like on your computer.

The test

Every lesson ends with Test yourself: five questions picked at random from a bank of 30 to 50 about that lesson. Some ask you to choose an answer, some ask what a piece of code prints, and some ask you to write code and run it. Get 4 of 5 right to pass, and the lesson is marked as done. If you don't pass, read the explanations, look at the lesson again, and take a new test: you get five different questions. You can also press Mark this lesson as done yourself.

Your progress stays in this browser

Finished lessons, test results, checkpoints and the files you write in the editor are saved in this browser, on this device only. There is no account and nothing is sent anywhere. That is why the progress bars and Continue where you left off know where you stopped. Open the academy in another browser or on another device and it starts fresh; clear your browser's site data and your progress is gone.

Where to start

You do not have to start at level 1. Pick the first row that describes you:

When a later lesson uses something you skipped, it links back to the lesson that teaches it. A quick way to find your gaps is the course checkpoint: take the checkpoint of a course you think you know. If you pass, move on; if you don't, the questions you missed tell you which lessons to read.

Practice

console.log("My name is Ada.");
console.log("I want to build:", "a booking API for my salon");

My name is Ada.
I want to build: a booking API for my salon

Recap

• A backend is the program on another computer that stores data, checks every request and answers the app. The academy teaches you to build one.
• The academy is 19 levels in six tracks: Thinking, JavaScript, TypeScript, Backend engineering, ZudoJS and Production. Each level is a course of modules and lessons. ZudoJS is the destination.
• You build the Task API (plain Node.js, then ZudoJS), the BookStore API in TypeScript, your own mini framework, and two capstones: ShopFlow and a SaaS platform.
• Tiers tell you what you must learn (Foundation, Core) and what you learn when you need it (Advanced, Production).
• Lesson pages have objectives, Reason it out boxes, runnable examples with real output, the editor, exercises and a test. Course pages end with a checkpoint of 20 questions: 16 to pass. Progress is saved in this browser only.
• Beginners start at the next lesson; other programmers at JavaScript; JavaScript developers at TypeScript; TypeScript backend developers at ZudoJS fundamentals.

Next, in Your developer environment, you meet the tools every developer uses: the terminal, a code editor and the browser's developer tools.