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Latest Updates

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 "<<"

👀 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? 🤔

ECMAScript 1 19 katas

Function constructor

Function.length #easy #in progress

Function.prototype #easy #in progress

new Function() and Function() #in progress

function API

function.arguments (as introduced in ES1) #easy #in progress

function.length (as introduced in ES1) #easy

function.prototype #easy #in progress

Bitwise Shift Operators

All bitwise shift operators #easy

Left Shift "<<"

Right Shift ">>"

Unary Operators

All unary operators #easy

Unary "+" operator

Unary "+" operator in depth

📕 What's an "Unary" Operator?

Type conversion

to number #in progress

Global Object API

parseInt() #easy

parseInt() in depth #easy #in progress

📕 Building the parseInt() Katas

Array API

array.sort() basics #easy

array.sort() can take a compare function

📕 Learning JavaScript Arrays

Object API

Object() (as introduced in ES1)

ECMAScript 3 2 katas

Array API

array.push() (as introduced in ES3)

array.shift() (as introduced in ES3) #easy

📕 Learning JavaScript Arrays

ECMAScript 5 4 katas

function API

function.arguments (as modified since ES5) #easy #in progress

function.bind()

function.length (with ES5 features) #easy

Strict mode

Turn strict mode on/off

📕 How to Control Strict Mode

ECMAScript 6 / ES2015 86 katas

Array API

array.entries()

array.findIndex()

array.values()

📕 Learning JavaScript Arrays

Class

creation #easy

extends #easy

static #easy

super in constructor

super in method

Generator

return inside a generator function

send function to a generator

send value to a generator

yield expressions

Destructuring

array #easy

defaults #easy

object #easy

string #easy

Promise

promise.catch()

basics #easy

chaining then()

String API

string.endsWith() #easy

string.includes() #easy

string.repeat(count) #easy

string.startsWith() #easy

Reflect

Reflect.apply()

Reflect.construct()

Reflect.defineProperty()

Reflect.getPrototypeOf()

basics #easy

Set

set.clear() #easy

set.delete() #easy

the API #easy

Map

map.has() #easy

basics #easy

Iterator

usage #in progress

Symbol

Symbol.hasInstance method #in progress

Symbol.keyFor()

Object literal

computed properties

getter #easy

setter #easy

Template strings

basics #easy

multiline #easy

tagged template strings

function API

function.length (with ES6 features)

function.name

function.name in depth #in progress

Number API

Number.isInteger() #easy

Number.isNaN() #easy

Number.parseInt() #easy

📕 Building the parseInt() Katas

Spread operator

Rest operator

with destructuring

Block scope

const declaration #easy

let declaration #easy

Arrow functions

basics #easy

function binding #easy

Modules

import statement #easy #in progress

Default parameters

basics #easy

Object API

Object.is() #easy

Unicode

ECMAScript 7 / ES2016 1 katas

Array API

array.includes() #easy

📕 Learning JavaScript Arrays

ECMAScript 8 / ES2017 3 katas

Object API

Object.entries() #easy #in progress

Object.values() #easy #in progress

Async Function

ECMAScript 10 / ES2019 12 katas

Array API

array.flat() #in progress

array.flatMap() #in progress

stable array.sort() #in progress

📕 Learning JavaScript Arrays

String API

string.trimEnd() #easy #in progress

string.trimStart() #easy

Object API

Object.fromEntries()

Object.fromEntries() in depth

try-catch

unbinded catch #easy #in progress

Symbol API

symbol.description #in progress

JSON superset

JSON superset basics #in progress

JSON API

well-formed JSON.stringify() #easy #in progress

Function API

function.toString() #easy #in progress

ECMAScript 11 / ES2020 3 katas

String API

string.matchAll()

string.matchAll() in depth #in progress

BigInt

basics #easy

ECMAScript 14 / ES2023 1 katas

Array API

array.toReversed() #easy

📕 Learning JavaScript Arrays