Learn JavaScript
five minutes at a time.

const name = "Pebble";
console.log(`Hello, ${name}!`);

Hello, Pebble!

The Codiqo JavaScript course starts at console.log() and covers let and const, strings, conditions, loops, arrays, objects, functions, classes, modules and async code, and ends with a flashcards app you build yourself.

How the JavaScript lessons work

The full JavaScript curriculum

1. Foundations

   Syntax, variables, types, output and expressions.

   First Steps: Write your first lines of JavaScript and store values in variables.

   • Hello, JavaScript: Print with console.log() and write strings with quotes
   • Numbers and Arithmetic: Calculate with + - * / and see the results
   • Variables with let and const: Name values with let and const, reuse and update them
   • typeof and Comments: Check types with typeof and explain code with comments

   Text and Numbers: Build and change strings and work with numbers.

   • Template Literals: Join strings with + and insert values with backticks and ${}
   • Reading and Changing Text: Use .length, indexes, slice(), toUpperCase(), trim() and replace()
   • Numbers and the Math Object: Use %, **, Math.round(), Math.max() and toFixed()
   • Precedence and Updates: Predict the order of operations and update values with ++ and +=

   Types and Logic: Convert between types and make true or false decisions.

   • Converting Types: Use Number(), String(), parseInt() and parseFloat()
   • Equality, null and undefined: Use === instead of == and represent missing values
   • Booleans and Logical Operators: Compare values and combine conditions with && || and !
   • Project: Eligibility Checker: Decide eligibility from several conditions

2. Logic and Repetition

   Conditions, loops, Boolean logic and control flow.

   Making Decisions: Run different code depending on conditions.

   • if and else: Run code only when a condition is true and provide an alternative path
   • else if and Nested Conditions: Choose between several options and put decisions inside decisions
   • Ternary and switch: Pick a value inline with ? : and choose between many exact values
   • Project: Grade Calculator: Convert scores into grades

   Loops: Repeat work with while and for.

   • while and for Loops: Repeat while a condition is true or a known number of times
   • break, continue and Direction: Count up and down, exit early and skip iterations
   • Running Totals and Searching: Accumulate a value in a loop and find whether something exists
   • Project: Countdown: Print a formatted countdown

   Patterns and Scope: Classic loop patterns and where variables live.

   • Nested Loops and Building Strings: Put loops inside loops and grow text inside a loop
   • Tracing Loops: Predict loop behaviour step by step and fix off-by-one errors
   • Block Scope: Understand where let and const are visible and avoid var surprises
   • Project: FizzBuzz: Solve the classic FizzBuzz problem

3. Data and Functions

   Arrays, objects, strings, functions and methods.

   Arrays: Store and process ordered lists of values.

   • Creating and Indexing Arrays: Write array literals and read and change items by position
   • Adding and Removing Items: Use push(), pop(), shift() and unshift()
   • Looping and Searching Arrays: Loop with for...of and search with includes() and indexOf()
   • Project: To-Do List: Manage a list of tasks

   Objects and Functions: Model things with objects and reuse code with functions.

   • Objects and Properties: Create objects and read and update them with dot and bracket notation
   • Nested Data: Combine arrays and objects and loop over keys and entries
   • Functions and Parameters: Write functions that take parameters and return results
   • Arrow Functions and Closures: Write compact functions with => and functions that remember values

   Array Methods and JSON: Transform data with methods and move it around as JSON.

   • map() and filter(): Transform every item and keep the items that match
   • reduce(), find() and sort(): Combine items into one value, find a match and sort correctly
   • Destructuring, Spread and JSON: Unpack and copy arrays and objects and convert data with JSON
   • Project: Grade Statistics: Summarise a list of scores

4. Applied JavaScript

   Errors, modules, asynchronous concepts, APIs and practical projects.

   Errors and Modules: Handle problems gracefully and split code into files.

   • Reading Error Messages: Find the cause of an error and recognise ReferenceError and TypeError
   • try...catch and throw: Handle errors, run clean-up code and signal problems of your own
   • import and export: Share code between modules and understand npm packages
   • Project: Safe Calculator: Build a calculator that never crashes

   Async and APIs: Code that waits without blocking, and data from the web.

   • setTimeout() and Callbacks: Understand the event loop and run code later
   • Promises, async and await: Represent future values and write async code that reads top to bottom
   • fetch() and JSON APIs: Request data from a URL, check status codes and handle failures
   • Project: Data Explorer: Load and summarise API data

   Capstone Project: Plan and build a complete JavaScript program.

   • Planning and Modelling: Turn an idea into a plan and choose structures for the program
   • Core Logic and the DOM: Implement the main logic and display data on a web page
   • Events and Testing: Respond to clicks and typing and check behaviour with tests
   • Polishing: Improve readability and output

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