You Can’t Learn JavaScript by Writing JavaScript?

Aug 13, 2024

This title sounds wrong on purpose.

Of course you learn JavaScript by writing JavaScript.

But if “writing” means copying patterns, stacking tutorials, and shipping code you can’t explain, then you’re not learning JavaScript—you’re learning how to produce JavaScript-shaped output.

Real understanding looks like this:

You can predict what the code will do before it runs.

That’s the skill that makes debugging possible, interviews calmer, and production incidents survivable.

The difference between typing and learning

When people say “just build projects,” they usually mean well.

But projects can accidentally become a hiding place. You can keep adding features while never learning:

  • the event loop
  • closures
  • async behavior
  • this
  • prototype chains
  • coercion
  • DOM event propagation

You don’t need to memorize every edge case.

You do need a mental model.

How to actually learn JavaScript faster

1) Practice prediction

Before running code, pause and write down what you think happens.

Then run it.

If you were wrong, don’t move on until you can explain why.

Here’s a tiny example:

console.log("A");

setTimeout(() => console.log("B"), 0);

Promise.resolve().then(() => console.log("C"));

console.log("D");

If you predict the output correctly, you’re building the event loop model.

2) Read code written by other humans

Writing is half the story. Reading is where you pick up:

  • naming
  • structure
  • boundaries
  • tradeoffs

Pick a small, well-written library and read it slowly. Even if you don’t understand everything, you’ll learn how experienced developers think.

3) Debug on purpose

Most learning happens when something breaks.

Create reps:

  • write a bug, then fix it
  • use the debugger (breakpoints, step over, watch variables)
  • read the stack trace top to bottom

The goal is not “never break.”

The goal is “recover quickly.”

4) Re-implement tiny primitives

Not to be clever—this is how you build intuition.

Try implementing:

  • map, filter, reduce
  • a tiny debounce function
  • a simple event emitter
  • a basic router (match "/users/:id")

You’ll learn more in two hours of this than in a week of copying.

5) Learn the language in layers

JavaScript isn’t one thing. It’s layers:

  • syntax and expressions
  • functions and scope
  • objects and prototypes
  • async and concurrency model
  • runtime environment (browser vs Node)
  • tooling (bundlers, transpilers)

Most confusion comes from mixing layers.

If a bug involves “why doesn’t this variable exist,” that’s scope. If it involves “why is this slow,” that’s runtime + performance. If it involves “why does this work locally but not in prod,” that’s environment/tooling.

6) Use AI the right way

AI can accelerate learning, but only if you keep ownership.

Good prompts:

  • “Explain this code like I’m new, then like I’m advanced.”
  • “Give me 5 edge cases to test.”
  • “Ask me questions until I find the bug.”

Bad prompts:

  • “Do my assignment.”
  • “Build the whole app.”

A practical study plan (2 weeks)

If you want structure, here’s a simple plan:

  • Days 1–3: scopes, closures, hoisting (prediction exercises)
  • Days 4–6: objects, this, prototypes (re-implement small pieces)
  • Days 7–9: async (Promise, async/await, event loop)
  • Days 10–12: DOM events + fetch + error handling
  • Days 13–14: build a small app with tests + intentional debugging

The punchline

Write code, yes.

But don’t confuse output with understanding.

If you want to learn JavaScript, optimize for:

  • prediction
  • debugging
  • reading
  • reflection

Do that and your JavaScript stops being “stuff you type” and becomes a tool you can actually control.