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Read it. Practise it. Know it.

MEPX brings together 119 short tests with a course behind each one, Python and JavaScript courses that run in your browser, an English tutor that checks every sentence you write, and books written for you by MEPX AI.

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or start the Python course

Tests · JavaScript fundamentals

Question 3 of 8About 6 min

What does const actually prevent?

1Reassigning the binding

2Changing an object it points to

3Both of those

4Neither of those

Next questionEnter continues

Reader · The Quiet River

Over ten thousand years the river had carved the valley into the shape it has today, one flood at a time.

carved · verb

Cut or shaped slowly, here by water wearing the rock away.

Saved to your vocabulary

Python course · Loops

PythonRun

for n in range(3):
    print("step", n)

step 0
step 1
step 2

tests across 11 subjects: 119tests across 11 subjects
questions, each explained: 947questions, each explained
short lesson chapters: 1,232short lesson chapters
coding chapters that run in your browser: 135coding chapters that run in your browser

One place to learn

Four ways in, whatever you want to learn.

Check what you know with a test, build a skill with a course, practise your English in conversation, or read your way into a new subject.

Tests

Short tests with a course behind each one

Read about 10 short chapters, then answer the quiz. Every question you miss comes back with the right answer and why it is right.

Answers reshuffled on every run
Keyboard friendly, no timer
Your best score is kept

Browse tests

Courses

Python and JavaScript, taught with code you run

114 Python chapters and 21 JavaScript chapters. Edit any example and run it on the page, with nothing to install.

Graded exercises per chapter
A quiz at the end of each course
Progress saved as you go

Open the courses

Tutor

Chat in English, with every sentence checked

Talk about anything you like. Each message is checked before it sends, and a mistake pauses the chat until you write it correctly.

Rewrite it your way, or take the fix
Your first-try accuracy is tracked
Chill, normal or strict checking

Start chatting

Reader

Books written for you, on any subject

Describe a book and MEPX AI writes it, pitched at the reader you choose. Tap any word to have it explained in context.

Up to ten pages per book
Tapped words become flashcards
A comprehension check at the end

Write a book

Try it now

Answer a question. See why.

These come straight from the tests. Pick an answer and you get the reason behind it, the same way every quiz on MEPX ends.

01Learn the ideasEach test opens with a short course. Read it in a few minutes, or skip straight to the questions.
02Test yourselfOne question per screen. Click, use the arrow keys or press a number, whichever is faster.
03Fix the gapsYour result lists every miss with the right answer and a one line reason, so the next run goes better.

Question 1 of 4JavaScript fundamentals

What does typeof null return in JavaScript?

Pick an answer to see whether you are right, and why.

Subjects

Pick a subject and start.

All 119 tests

114 chapters · runs in your browser

Python course

From your first print to classes, files and the standard library, with exercises that check your code.

def greet(name):    return f"Hello, {name}"

Start the course

21 chapters · runs in your browser

JavaScript course

The language the browser runs, from your first script to types, operators and how equality really works.

const total = [1, 2, 3]  .reduce((a, b) => a + b);

Start the course

Start with one test. It takes about six minutes.

No sign up and nothing to install. Your scores, books and progress stay in your own browser.

Browse tests See the courses