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Learn JavaScript – In Depth

Topics 56 katas

String API 6

string.endsWith()
string.includes()
string.repeat(count)
string.startsWith()
string.trimEnd() #in progress
string.trimStart()

function API 5

function.arguments (as introduced in ES1) #in progress
function.arguments (as modified since ES5) #in progress
function.length (as introduced in ES1)
function.length (with ES5 features)
function.prototype #in progress

Destructuring 4

array
defaults
object
string

Array API 4

array.includes()
array.shift() (as introduced in ES3)
array.sort() basics
array.toReversed()

Object API 4

Object.groupBy() #new
Object.entries() #in progress
Object.is()
Object.values() #in progress

Number API 3

Number.isInteger()
Number.isNaN()
Number.parseInt()

Set 3

set.clear()
set.delete()
the API

Class 3

creation
extends
static

Arrow functions 2

basics
function binding

Block scope 2

const declaration
let declaration

Global Object API 2

parseInt()
parseInt() in depth #in progress

Function constructor 2

Function.length #in progress
Function.prototype #in progress

Template strings 2

basics
multiline

Object literal 2

getter
setter

Map 2

map.has()
basics

BigInt 1

basics

Function API 1

function.toString() #in progress

JSON API 1

well-formed JSON.stringify() #in progress

try-catch 1

unbinded catch #in progress

Default parameters 1

basics

Modules 1

import statement #in progress

Unary Operators 1

All unary operators

Bitwise Shift Operators 1

All bitwise shift operators

Reflect 1

basics

Promise 1

basics

👀 You're a newbie, JSKatas takes you by the hand and helps you learn at your speed! Start with an easy kata to get the hang of it and find out if you like it. For example learn how to declare a variable.

🧛🏼 You're a seasoned pro, discover hidden JavaScript gems 💎.
For example: Do you know all three bitwise shift operators? 🤔

Latest Updates

October 18th, 2024
🥋 The first Proxy basics kata inspired by the 76th #JSLang meetup
March 29th, 2024
🥋 I released Learning JavaScript Arrays.
Let me know what you think.
March 28th, 2024
🥋 The first array.push() kata gave me so many
more ideas for katas on arr.push(), it's a 🐇 hole.
March 27th, 2024
🆕 The first kata on Object() constructor as a function
January 16th, 2024
🆕 🍉 First ES14/ES2023 kata array.toReversed()
November 7th, 2023
🆕 First type-conversion kata "to boolean"
November 5th, 2023
🆕 9 new katas around functions 🤯.
🔥 The first strict mode kata.
👷🏽‍♀️ Each test runs in a separate worker thread now,
this allows for more test cases to be written.
October 15th, 2023
🆕 NEW: function.name kata.
🌟 Two katas in progress: Symbol.hasInstance and function.name in depth.
October 14th, 2023
✨ Add 'How to' on the kata pages.
🧹 Improved class-creation kata. Explains better, covers more knowledge.
Two new katas: 🆕 function.length for ES1 and 🆕 with ES6 features.
October 11th, 2023
🆕 array.shift() first introduced in 1999, has a kata now.
The kata for let is now in GIVEN-WHEN-THEN style for better usability.
October 9th, 2023
🐞 Bugfix: Make the let kata work again, it runs in a worker thread now (see issue).
October 8th, 2023
🆕 New kata: String.raw.
September 30th, 2023
Dive into JavaScript arrays — the first in-depth article in our series!
September 29th, 2023
Configure the behavior on the kata site, turn on/off the auto-open of the first kata, and more.
September 26th, 2023
🎉 🎉 🎉 A Big Change. 🎉 🎉 🎉
Now you can solve the katas inline without going to tddbin.
September 4th, 2023
🆕 New kata Bitwise Shift Operators: Right Shift ">>"
🆕 New kata All bitwise shift operators
September 1st, 2023
🆕 New kata Bitwise Shift Operators: Left Shift "<<"