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Learn JavaScript – In Depth

ECMAScript 1 19 katas

Function constructor 3

new Function() and Function() #in progress

Function.length #easy #in progress

Function.prototype #easy #in progress

function API 3

function.length (as introduced in ES1) #easy

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

function.prototype #easy #in progress

Bitwise Shift Operators 3

Left Shift "<<"

Right Shift ">>"

All bitwise shift operators #easy

Unary Operators 4

All unary operators #easy

Unary "+" operator

Unary "+" operator in depth

📕 What's an "Unary" Operator?

Type conversion 2

to number #in progress

Global Object API 3

parseInt() #easy

parseInt() in depth #easy #in progress

📕 Building the parseInt() Katas

Array API 3

array.sort() basics #easy

array.sort() can take a compare function

📕 Learning JavaScript Arrays

Object API 1

Object() (as introduced in ES1)

ECMAScript 3 2 katas

Array API 3

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

array.push() (as introduced in ES3)

📕 Learning JavaScript Arrays

ECMAScript 5 4 katas

function API 3

function.bind()

function.length (with ES5 features) #easy

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

Strict mode 2

Turn strict mode on/off

📕 How to Control Strict Mode

ECMAScript 6 / ES2015 87 katas

Array API 9

array.findIndex()

array.entries()

array.values()

📕 Learning JavaScript Arrays

Class 7

creation #easy

static #easy

extends #easy

super in method

super in constructor

Generator 6

yield expressions

send value to a generator

send function to a generator

return inside a generator function

Destructuring 6

array #easy

string #easy

object #easy

defaults #easy

Promise 5

basics #easy

chaining then()

promise.catch()

String API 5

string.includes() #easy

string.repeat(count) #easy

string.startsWith() #easy

string.endsWith() #easy

Reflect 5

basics #easy

Reflect.apply()

Reflect.getPrototypeOf()

Reflect.construct()

Reflect.defineProperty()

Set 5

set.delete() #easy

the API #easy

set.clear() #easy

Map 5

basics #easy

map.has() #easy

Iterator 4

usage #in progress

Symbol 4

Symbol.keyFor()

Symbol.hasInstance method #in progress

Object literal 4

computed properties

getter #easy

setter #easy

Template strings 4

basics #easy

multiline #easy

tagged template strings

function API 3

function.length (with ES6 features)

function.name

function.name in depth #in progress

Number API 4

Number.isInteger() #easy

Number.isNaN() #easy

Number.parseInt() #easy

📕 Building the parseInt() Katas

Spread operator 2

Rest operator 2

with destructuring

Block scope 2

let declaration #easy

const declaration #easy

Arrow functions 2

basics #easy

function binding #easy

Proxy 1

basics #new

Modules 1

import statement #easy #in progress

Default parameters 1

basics #easy

Object API 1

Object.is() #easy

Unicode 1

ECMAScript 7 / ES2016 1 katas

Array API 2

array.includes() #easy

📕 Learning JavaScript Arrays

ECMAScript 8 / ES2017 3 katas

Object API 2

Object.entries() #easy #in progress

Object.values() #easy #in progress

Async Function 1

ECMAScript 10 / ES2019 12 katas

Array API 4

array.flat() #in progress

array.flatMap() #in progress

stable array.sort() #in progress

📕 Learning JavaScript Arrays

String API 2

string.trimStart() #easy

string.trimEnd() #easy #in progress

Object API 2

Object.fromEntries()

Object.fromEntries() in depth

try-catch 1

unbinded catch #easy #in progress

Symbol API 1

symbol.description #in progress

JSON superset 1

JSON superset basics #in progress

JSON API 1

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

Function API 1

function.toString() #easy #in progress

ECMAScript 11 / ES2020 3 katas

String API 2

string.matchAll()

string.matchAll() in depth #in progress

BigInt 1

basics #easy

ECMAScript 14 / ES2023 1 katas

Array API 2

array.toReversed() #easy

📕 Learning JavaScript Arrays

ECMAScript 15 / ES2023 1 katas

Object API 1

Object.groupBy() #easy #new

👀 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 "<<"