Can you still read code?

155 JavaScript questions that look easy and aren't. Use your brain, choose an answer, learn why.

What's the output?

function sayHi() {
  console.log(name);
  console.log(age);
  var name = 'Lydia';
  let age = 21;
}

sayHi();

Pick one. It counts as your answer in the game.

Know what the code does.

Agents write most of the code now, faster than anyone can review it. So we write less, read less, and slowly forget things we used to know.

Put the agent aside for a few minutes. Each question is a few lines of JavaScript with one right answer and a short explanation: a small workout for your memory and your mental model of the language.

The questions and explanations are Lydia Hallie's javascript-questions (opens in a new tab), used under the MIT licence. Every card links to its original. This app is open source: add a question (opens in a new tab).