How to build · 02

Programming Fundamentals

Variables, conditions, functions, data structures, algorithms, OOP, Git, the terminal, HTTP and debugging.

Read: 0 / 15Web Basics Programming Basics Variables & Data Types Conditions & Loops Functions Data Structures Algorithms Object-Oriented Programming Terminal & CLI Git & GitHub HTTP & JSON API Fundamentals Debugging Error Handling

Web Basics

Fundamentals✓
How a website works: frontend, backend and database in plain words
A website has three parts. The frontend is what visitors see and click in the browser; the backend is a program on the server that receives requests, checks data and decides what to answer; the database stores products, requests and users. A simple brochure site can live without a backend and database. Anything that has to “remember” data — a catalogue, a customer account, an admin panel — needs storage and server-side logic, but you do not have to write them from scratch: BaaS platforms such as Supabase or Firebase and external services with an API provide them, and one visitor’s settings can be kept right in the browser.
Beginner · 7 min read

Programming Basics

Tutorial✓
Your first JavaScript program: how code turns into action
A program is a set of instructions the computer runs in order: it takes data, computes something and outputs a result. You can run JavaScript with nothing installed, in the browser console (Ctrl+Shift+J in Chrome and Edge), or from a file with node file-name.js once Node.js is installed. The first useful program in this lesson is a tip calculator: the bill goes in, the tip and the total come out.
Beginner · 9 min read · practice ~45–90 min

Variables & Data Types

Fundamentals✓
Variables and data types
A variable is a name under which a program stores a value: in JavaScript you declare it with const if the value won't be reassigned and with let if it will. Every value has a type: seven primitive ones (number, string, boolean, undefined, null, bigint, symbol) plus objects, arrays included. You check the type with the typeof operator and compare values with strict === so JavaScript doesn't convert types behind your back.
Beginner · 7 min read

Conditions & Loops

Tutorial✓
Conditions and loops
Conditions let a program choose what to do: if runs a block only when an expression is true, else if and else cover other cases, and switch is handy for choosing by a single value. Loops repeat an action: for a set number of times, for...of for every array element, while as long as a condition holds. Every loop needs an exit condition, or the program hangs.
Beginner · 7 min read · practice ~45–90 min

Functions

Tutorial✓
Functions: parameters, return values, scope
A function is a named block of code that takes data through parameters, does something and returns a result with return; without return it returns undefined. In JavaScript you can declare a function with function, write it as an expression or as an arrow function (a, b) => a + b. Variables declared inside a function aren't visible outside it, and a nested function remembers the outer function's variables even after it has finished; that's called a closure.
Beginner · 6 min read · practice ~45–90 min

Data Structures

Fundamentals✓
Arrays, objects, Map and Set: data structures in practice
A data structure is a way of storing values so that the operation you need is simple and fast. In JavaScript, an array holds an ordered list, an object holds a record with known fields, a Map is a dictionary with keys of any type, and a Set is a collection of unique values with a fast "is it there" check. The choice starts with one question: how will you look the data up — by position, by field name, by an arbitrary key or by the value itself?
Beginner · 8 min read

Algorithms

Fundamentals✓
Algorithms and complexity: Big O without fear
Algorithmic complexity describes how the number of steps or the memory grows as the input grows. It is written in Big O notation: O(n) means roughly as many steps as elements, O(n²) means every element is compared with every other, O(log n) means each step discards half of the data. On 50 test records the difference is invisible; on 100,000 it turns milliseconds into seconds, and the usual fix is the right data structure — a Set or Map instead of searching an array.
Intermediate · 7 min read

Object-Oriented Programming

Fundamentals✓
OOP: classes, encapsulation, inheritance and composition
Object-oriented programming (OOP) combines data and behavior into objects: an order knows its own contents and the rules for changing them. A class describes such objects, # private fields hide state, inheritance reuses shared logic through extends and super, and composition assembles behavior from small independent objects. In practice, inheritance suits small, stable hierarchies, and composition suits almost everything else.
Intermediate · 7 min read

Terminal & CLI

Tutorial✓
Terminal and command line for developers
A terminal is the window for text commands; a shell (bash, zsh, PowerShell) is the program that reads and runs them. A developer needs about a dozen commands: change directory (cd), list contents (ls), create and delete files, run node or npm, set an environment variable and chain commands with a pipe. Below are all of these steps with real output and PowerShell equivalents for Windows.
Beginner · 10 min read · practice ~45–90 min

Git & GitHub

HTTP & JSON

Fundamentals✓
HTTP and JSON: requests, responses, headers and data format
An HTTP request is a text message made of a method, a target, headers and an optional body; a response is a status code, headers and a body. JSON is the format the body usually carries: objects, arrays, double-quoted strings, numbers, true, false and null. To work with APIs confidently you need three things: what a method means (is it safe, can it be retried), what the status code class says, and which Content-Type describes the body.
Beginner · 9 min read

API Fundamentals

Fundamentals✓
What is an API in plain words and why a business needs one
An API is an agreed way for one program to ask another to do something or hand over data: your website asks the payment service “has this order been paid?” and gets an answer in a machine-readable format. A business needs APIs so its systems — website, 1C, CRM, marketplace, messengers — exchange data on their own, without manual copying. Before an integration, find out where the access keys are stored, what happens when something fails and who watches the limits.
Beginner · 7 min read

Debugging

How-to✓
Debugging: breakpoints, console and reading a stack trace
Debugging is testing hypotheses, not trying random edits: reproduce the bug, narrow down where it happens and confirm the cause with facts. A stack trace is read top-down: the first line is the error type and message, and the first at line pointing to your file is where the program failed. When nothing throws but the result is wrong, set a breakpoint and inspect variables at run time — in Chrome DevTools, VS Code or via node --inspect.
Beginner · 7 min read · practice ~30–60 min

Error Handling

Fundamentals✓
Error handling: try/catch, async errors and clear messages
Handle an error where you have something to say about it: low-level code throws a specific error of its own class and keeps the original in cause, while the boundary — a request handler, a screen, a command — catches it, logs the details and shows the user a short message about what to do. In async code every promise must be awaited or have a .catch(): in Node.js an unhandled rejection terminates the process by default. An empty catch that swallows the error is worse than a crash.
Intermediate · 7 min read

Learning paths with this direction

JavaScript from scratch · 9 →Markup and layout: HTML and CSS · 7 →Java · 6 →Spring Boot · 7 →Docker and deployment · 8 →APIs and integrations · 8 →← All directions

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