JavaScript

1

Variables and data types

6 lessons · 27 min

1. 1 Declaring variables Learn to declare variables with let, const and var and the basic differences between them. 4 min
2. 2 Difference between const and let Learn reassignment and immutability concepts. 5 min
3. 3 First data types Learn the basic data types number, string and boolean and the primitive concept. 4 min
4. 4 Difference between null and undefined Learn the difference between empty and undefined values and when to use each. 5 min
5. 5 The typeof operator Learn how to check a variable's type with typeof and its pitfalls. 4 min
6. 6 Summary - Variables and types Combine variable declaration and data types to write a small profile card. 5 min

2

Operators

6 lessons · 29 min

1. 1 Arithmetic operators Learn basic arithmetic with +, -, *, /, % and ** operators. 4 min
2. 2 Assignment operators Learn shortcut assignments with =, +=, -=, ++ and --. 5 min
3. 3 Comparison operators Learn to compare values with ==, ===, !=, <, >, <= and >=. 5 min
4. 4 Logical operators Learn boolean logic and short-circuit evaluation with &&, || and !. 5 min
5. 5 Operator precedence Learn how operation order is determined and how to change precedence with parentheses. 5 min
6. 6 Summary - Operators Combine arithmetic, comparison and logical operators to build a grade calculator. 5 min

3

Conditionals

6 lessons · 28 min

1. 1 The if statement Learn how to check a condition with if and the code block. 4 min
2. 2 else and else if Learn else and else if chains for alternative cases. 5 min
3. 3 The switch statement Learn multi-way selection with switch, case, break and default. 5 min
4. 4 The ternary operator Learn to write a conditional expression in one line with ? :. 4 min
5. 5 Comparison pitfalls Learn the difference between === and == and type coercion pitfalls. 5 min
6. 6 Summary - Conditionals Build a day-of-the-week app using if, switch and the ternary operator. 5 min

4

Numbers and Math

6 lessons · 28 min

1. 1 Integers and decimals Learn integer and decimal numbers and that JavaScript has a single number type. 4 min
2. 2 The Math object Learn rounding with Math.round, Math.floor and Math.ceil. 5 min
3. 3 Math.random and Math.min/max Learn to generate random numbers and use Math.min/Math.max for bounds. 5 min
4. 4 NaN and Infinity Learn what NaN and Infinity mean and how to check for them. 4 min
5. 5 Converting to numbers Learn to convert strings to numbers with parseInt, parseFloat and Number(). 5 min
6. 6 Summary - Numbers and Math Build a dice roll simulation using Math methods. 5 min

5

Project: CalculatorProject

5 lessons · 25 min

1. 1 Project: Calculator Overview of the 5-lesson calculator project: you will operate on two numbers and an operator. 4 min
2. 2 Number input and operator selection Take two numbers and an operator from the user to set up the operation. 5 min
3. 3 Computing the operation Use switch to select the operator and compute the result. 5 min
4. 4 Handling error cases Add guards for division by zero and invalid operator. 5 min
5. 5 Project final - Calculator Combine all parts and finalize a working calculator. 6 min

6

String basics

6 lessons · 26 min

1. 1 Creating strings Learn to create strings with single and double quotes and the difference between them. 4 min
2. 2 length and character access Learn the length property and accessing characters with brackets. 4 min
3. 3 String concatenation Learn to concatenate strings with + and the common mistakes around it. 4 min
4. 4 Template literals Learn template literals with backticks and using expressions inside ${}. 5 min
5. 5 Escape sequences Learn how to write special characters inside strings with \n, \t, \\ and \'. 4 min
6. 6 Summary - String basics Build a greeting message combining strings, concatenation and template literals. 5 min

7

Loops

6 lessons · 28 min

1. 1 The for loop Learn the for loop structure: counter, condition and increment steps. 5 min
2. 2 The while loop Learn the while loop that runs as long as the condition is true. 4 min
3. 3 The do...while loop Learn do...while that runs at least once and how it differs from while. 4 min
4. 4 break and continue Learn to exit a loop with break and skip an iteration with continue. 5 min
5. 5 Nested loops Learn to traverse structures like tables and matrices with nested loops. 5 min
6. 6 Summary - Loops Print a multiplication table using for and while loops. 5 min

8

Array basics

6 lessons · 28 min

1. 1 Creating and accessing arrays Learn to create array literals and access elements by index. 4 min
2. 2 Adding elements to arrays Learn to add elements to the end and start of an array with push and unshift. 5 min
3. 3 Removing elements from arrays Learn to remove elements from the end and start of an array with pop and shift. 5 min
4. 4 length and index relationship Learn the length property and how to access the last element. 4 min
5. 5 Multidimensional arrays Learn to create matrix-like structures with nested arrays. 5 min
6. 6 Summary - Array basics Build a queue app using push, pop, shift and unshift. 5 min

9

Functions

6 lessons · 28 min

1. 1 Defining and calling functions Learn to define and call functions with the function keyword. 4 min
2. 2 The return statement Learn to return a value from a function and early return. 4 min
3. 3 Parameters and arguments Learn the difference between parameters and arguments. 5 min
4. 4 Function expressions Learn the anonymous function expression assigned to a variable. 5 min
5. 5 Scope basics Learn why variables declared inside a function are not accessible from outside. 5 min
6. 6 Summary - Functions Write a VAT calculation function and call it with different amounts. 5 min

10

Project: Shopping cartProject

5 lessons · 25 min

1. 1 Project: Shopping cart Overview of the 5-lesson shopping cart project: add products and compute the total. 4 min
2. 2 Defining the product list Set up the cart foundation with arrays of product names and prices. 5 min
3. 3 Adding products to the cart Add products to the cart with push and list them with a loop. 5 min
4. 4 Computing the total Sum each product's price with a loop to find the cart total. 5 min
5. 5 Project final - Shopping cart Finalize the cart app showing the added products and the total amount. 6 min

11

Array iteration

6 lessons · 28 min

1. 1 Looping with forEach Learn to traverse an array with forEach and the callback idea. 5 min
2. 2 The for...of loop Learn to iterate over array values with for...of. 4 min
3. 3 Searching with indexOf Learn to find an element's position with indexOf. 5 min
4. 4 Checking with includes Learn to check whether an element is in the array with includes. 4 min
5. 5 findIndex and some Learn findIndex for the first matching index and some for any match. 5 min
6. 6 Summary - Array iteration Print a task list using forEach and for...of. 5 min

12

Array transformations

6 lessons · 31 min

1. 1 Transforming with map Learn to transform each element and create a new array with map. 5 min
2. 2 Filtering with filter Learn to select elements matching a condition with filter. 5 min
3. 3 Finding with find Learn to return the first matching element with find. 5 min
4. 4 some and every Learn some for any match and every for all matching. 5 min
5. 5 Reducing with reduce Learn to reduce an array to a single value and the accumulator idea. 6 min
6. 6 Summary - Array transformations Compute a class grade average with map, filter and reduce. 5 min

13

Objects

6 lessons · 30 min

1. 1 Creating objects Learn to create objects with key-value pairs using object literals. 5 min
2. 2 Property access Learn dot and bracket notation for property access and when to use each. 5 min
3. 3 Adding and changing properties Learn to add new properties and change existing ones. 5 min
4. 4 Defining methods Learn to define methods inside an object and the shorthand syntax. 5 min
5. 5 The this keyword Learn what this refers to inside a method and how it works. 5 min
6. 6 Summary - Objects Build a bank account app using objects and methods. 5 min

14

Project: Quiz appProject

5 lessons · 25 min

1. 1 Project: Quiz app Overview of the 5-lesson quiz project: define questions and compute the score. 4 min
2. 2 Defining question objects Build an array of objects holding question, options and correct answer. 5 min
3. 3 Showing questions and getting answers Show questions one by one with for...of and collect answers. 5 min
4. 4 Computing the score Check the answer with if and increment the score counter. 5 min
5. 5 Project final - Quiz Finalize the quiz app and display the total score. 6 min

15

Parameters

6 lessons · 29 min

1. 1 Default parameters Learn what happens with missing arguments by setting default parameter values. 5 min
2. 2 The rest parameter Learn to collect unlimited arguments as an array with ...args. 5 min
3. 3 The arguments object Learn the legacy arguments object you often see in old code and why rest is preferred. 4 min
4. 4 Return value types Learn to return numbers, arrays and objects and how to return multiple values. 5 min
5. 5 Helper functions Learn to break a big problem into small helper functions. 5 min
6. 6 Summary - Parameters Write a flexible order summary function using default and rest parameters. 5 min

16

Boolean logic

6 lessons · 29 min

1. 1 Boolean values Learn true and false values and expressions that return booleans. 4 min
2. 2 Short-circuit evaluation Learn how && and || short-circuit values and the patterns based on it. 5 min
3. 3 Nullish coalescing Learn to give a default for null and undefined with the ?? operator. 5 min
4. 4 Optional chaining Learn to safely access null and undefined values with ?. 5 min
5. 5 Logical assignment Learn shortcut logical assignments with &&=, ||= and ??=. 5 min
6. 6 Summary - Boolean logic Write a safe user profile fetcher using short-circuit, nullish and optional chaining. 5 min

17

Type conversion

6 lessons · 30 min

1. 1 Explicit type conversion Learn explicit type conversion with String(), Number() and Boolean(). 5 min
2. 2 Implicit type coercion Learn how implicit type coercion works with +, == and in if conditions. 5 min
3. 3 Difference between == and === Learn equality operators that do and do not perform type conversion. 5 min
4. 4 Truthy and falsy values Learn which values are considered false and which are true in a boolean context. 5 min
5. 5 Common conversion pitfalls Learn common number-conversion mistakes and how to avoid them. 5 min
6. 6 Summary - Type conversion Write a function that safely converts user input to numbers using type conversion. 5 min

18

Project: To-do listProject

5 lessons · 25 min

1. 1 Project: To-do list Overview of the 5-lesson to-do project: manage tasks as objects. 4 min
2. 2 Designing the task object Design a task object holding id, title and completion state. 5 min
3. 3 Adding and listing tasks Add tasks with push and display them with for...of. 5 min
4. 4 Completing and deleting tasks Find a task with findIndex to complete it and remove it with filter. 5 min
5. 5 Project final - To-do list Finalize the to-do app and make all commands work. 6 min

19

Advanced string methods

6 lessons · 29 min

1. 1 slice and substring Learn to slice parts of a string with slice and substring. 5 min
2. 2 replace and replaceAll Learn to change the first match with replace and all matches with replaceAll. 5 min
3. 3 split and join Learn to convert a string to an array with split and back with join. 5 min
4. 4 trim, padStart, padEnd Learn to trim whitespace and pad a string to a length with padStart/padEnd. 5 min
5. 5 Case and includes Learn string operations with toUpperCase, toLowerCase and includes. 4 min
6. 6 Summary - Advanced string methods Build a function that reverses a sentence word by word using split, map and join. 5 min

20

Console methods

6 lessons · 28 min

1. 1 console.log basics Learn to log output and pass multiple arguments with console.log. 4 min
2. 2 console.warn and console.error Learn warn and error methods for warning and error messages. 4 min
3. 3 Tables with console.table Learn console.table to display arrays and objects as tables. 5 min
4. 4 console.group and groupEnd Learn to group console output and create nested groups. 5 min
5. 5 Timing with console.time Learn to measure an operation's duration with console.time and timeEnd. 5 min
6. 6 Summary - Console methods Print a dataset neatly using console.group and console.table. 5 min

21

Errors

6 lessons · 30 min

1. 1 try...catch basics Learn to catch errors with try and catch and prevent the app from crashing. 5 min
2. 2 Throwing errors with throw Learn to throw your own errors and when to use it. 5 min
3. 3 The Error object Learn the Error object's message and name properties and how to create one. 5 min
4. 4 The finally block Learn finally for cleanup code that runs whether or not an error occurred. 5 min
5. 5 Common error types Recognize common error types like TypeError, RangeError and ReferenceError. 5 min
6. 6 Summary - Errors Safely handle a division by zero using try/catch/finally and throw. 5 min

22

Debugging

6 lessons · 29 min

1. 1 What is debugging? Learn the debugging process and effective approaches. 4 min
2. 2 Call traces with console.trace Learn to see a function's call stack with console.trace. 5 min
3. 3 The debugger statement Learn to pause code and step through it in DevTools with the debugger statement. 5 min
4. 4 Checking with console.assert Learn to log an error when a condition fails with console.assert. 5 min
5. 5 Common bug patterns Recognize common bugs like off-by-one, undefined access and wrong comparison. 5 min
6. 6 Summary - Debugging Test a calculation function using console.assert and console.trace. 5 min

23

Beginner finalFinal

5 lessons · 30 min

1. 1 Challenge - Calculator Combine arithmetic operators, conditionals and functions to write a calculator function. 6 min
2. 2 Challenge - Array operations Compute total revenue from a store's sales list with arrays, loops and reduce. 6 min
3. 3 Challenge - Object management Build a library book app with objects, properties and methods. 6 min
4. 4 Challenge - String operations Build a text formatting tool with string methods and template literals. 6 min
5. 5 Challenge - Error handling Write a function that validates age using try/catch and throw. 6 min