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Vibe Coding · レッスン

大きなタスクを手順に分解する

機能をプロンプトで扱える単位に分解します。

レッスン 3/413 ステップ

「大きなタスクを手順に分解する」はCoddyKit上の無料Vibe Codingレッスンです。 これはレッスン3/4です。 下記で完全なレッスンを無料で読むことができます。その後、ブラウザ内の組み込みコードエディタと24時間対応のAIチューターでハンズオン演習できます。 これはVibe Coding学習パスの一部であり、ウェブとCoddyKitアプリ全体で進捗が同期されます。 Vibe Codingコースには全4レッスンが含まれています。

このレッスンの一部はまだ翻訳されておらず、英語で表示されています。

Big Tasks Break AI

Ask AI to "build me a todo app with login, a database, and dark mode" in one prompt and you'll often get a tangled mess — half-finished, buggy, impossible to review. AI, like people, does its best work on one clear thing at a time.

The skill in this lesson is decomposition: breaking a big feature into small, promptable chunks you build and verify one by one.

Why Small Steps Win

Building in small steps with AI gives you huge advantages:

  • Reviewable — you can actually read 20 lines, not 500.
  • Testable — run each piece and confirm it works before moving on.
  • Recoverable — if step 3 breaks, steps 1–2 are still safe.
  • Steerable — you correct course early, not after a giant mess.

Small steps are how pros ship reliable apps with AI.

Plan First, Then Prompt

Before writing code, have the AI help you plan. Ask it to break your feature into a numbered list of steps. You're not building yet — you're getting a roadmap you can follow and reorder.

This planning prompt costs one message and saves you from building the wrong thing.

You are a senior engineer. Don't write code yet. I want to build a 'save favorite articles' feature for my web app. Break this into a numbered list of small, buildable steps, from simplest to most complete. Keep each step to one clear task.

A Good Decomposition

A solid plan turns one scary feature into a checklist. For our "favorites" feature, the AI might return:

  • 1. Add a star button to each article card.
  • 2. Toggle the star's filled/empty state on click.
  • 3. Store the favorited IDs in the browser.
  • 4. Load saved favorites when the page opens.
  • 5. Add a "My Favorites" view that filters the list.

Now each line is its own small prompt.

Prompt One Step at a Time

With the plan in hand, build step 1 only. Tell the AI explicitly to stop there. This keeps the output small and focused.

Notice the constraint: only this step. That prevents the AI from racing ahead and writing the whole feature in one unreviewable blob.

We're following our plan. Build ONLY step 1: add a star button to each article card. Use vanilla JS and HTML. Don't implement saving or toggling yet — just render the button. Return only the code for this step.

Verify Before You Continue

After each step, run it and check. Does the button appear? Good — move on. Broken? Fix this step before adding more. Stacking new code on a broken foundation is how vibe-coded apps fall apart.

Here's a tiny, self-contained piece of step 2 logic — toggling a saved state — that you could verify on its own.

// Step 2 logic, tested in isolation
function toggleFavorite(savedIds, id) {
  if (savedIds.includes(id)) {
    return savedIds.filter((x) => x !== id);
  }
  return [...savedIds, id];
}

let ids = [];
ids = toggleFavorite(ids, 7);
console.log(ids);
ids = toggleFavorite(ids, 7);
console.log(ids);

Carry Context Between Steps

Each new step depends on the last. When you prompt for step 2, remind the AI what step 1 produced — paste the relevant code or describe it. In agentic tools like Claude Code or Cursor, the AI can see your files, so just point at them.

Without this context, the AI may invent different names and break the connection between steps.

Now build step 2: toggle the star when clicked. Here is the button from step 1 so you match its class and structure:

<button class="star-btn" data-id="42">☆</button>

Write the click handler that switches between ☆ and ★. Return only the JS for this step.

The Vertical Slice Approach

Another way to decompose: build one tiny end-to-end slice first, then widen it. Instead of building the whole UI, then the whole backend, make ONE feature work all the way through — then add the rest.

  • Slice 1: favorite a single hard-coded article, save it, reload it.
  • Then: apply that working flow to all articles.

A thin working slice beats many half-built layers.

Let's build the thinnest working version first. Make ONLY this work end-to-end: clicking a star on one article saves its id to localStorage and re-reading localStorage shows it's saved. Skip the UI polish and the favorites page for now.

Decomposing in App Builders

Even in prompt-to-app tools like Bolt, v0 and Lovable, small steps win. Generate the first screen, preview it, then ask for the next change. Don't request the entire app in your opening prompt.

  • Prompt 1: "A landing page with a hero and a sign-up button."
  • Prompt 2: "Now add a pricing section below the hero."
  • Prompt 3: "Make the sign-up button open a modal."

You build a real app through a conversation, not one giant ask.

Keep a Running Checklist

Track your steps so you and the AI stay aligned. Keep a simple checklist in your prompt or a notes file and mark progress. This becomes the shared memory of your build.

In Claude Code, a TODO.md or CLAUDE.md works great — the agent reads it and knows what's done and what's next.

Here is our progress. Continue from the first unchecked item.

[x] 1. Star button on each card
[x] 2. Toggle star on click
[ ] 3. Save favorited IDs to localStorage
[ ] 4. Load favorites on page open
[ ] 5. 'My Favorites' filter view

Build step 3 only.

Knowing When to Split Further

If the AI's output for one "step" is still large or buggy, that step was too big — split it again. Signs a step needs breaking down:

  • The answer is hundreds of lines.
  • It touches many files at once.
  • You can't tell if it works by reading it.

There's no shame in tiny steps. The smaller the step, the more control you keep.

Quick Check

You ask AI to build a whole feature at once and get 400 lines you can't follow. What's the best next move?

対話的なレッスンで答える

Recap: Build in Steps

Decomposition is how you tame big builds with AI:

  • Have the AI plan the feature as a numbered list first.
  • Prompt one step at a time and tell it to stop there.
  • Run and verify each step before moving on.
  • Carry context forward and keep a checklist.
  • Prefer a thin end-to-end slice, and split further when a step gets too big.

Next: pinning the exact tech stack and style so AI builds it your way.

無料で開始

AI チューターと学ぶ JavaScript — 無料

ブラウザでリアルコードを書いて実行し、24/7 の AI チューターから瞬時にサポートを受け、ウェブまたはアプリで続きから学習できます。

コース
25
レッスン
100
無料で学習を始めるコース全体を表示

よくある質問

「大きなタスクを手順に分解する」レッスンは無料ですか？

はい。「大きなタスクを手順に分解する」の完全なテキストはこのウェブで無料で読めます。インタラクティブに演習し（組み込みコードエディタと24時間対応のAIチューター）、Vibe Codingコースの残りをアンロックするには、CoddyKit PROにアップグレードしてください。 Vibe Codingコースには全4レッスンが含まれています。

「大きなタスクを手順に分解する」で何を学びますか？

機能をプロンプトで扱える単位に分解します。 ブラウザで直接実行するハンズオンコードでVibe Codingを演習し、24時間対応のAIチューターがレッスンを進める中での質問に答えます。

Vibe Codingを始めるのに経験は必要ですか？

事前経験は必要ありません。CoddyKitのVibe Codingは初級者から上級者向けに構成されているため、ここから始めるか最初から始めて、自分のペースで進むことができます。 これはレッスン3/4です。

「大きなタスクを手順に分解する」レッスンにはどのくらい時間がかかりますか？

ほとんどのCoddyKitレッスンは約5～10分かかります。各レッスンはコンパクトでインタラクティブなので、着実に進歩し、ウェブとアプリ全体で正確に前回の場所から再開できます。

このVibe Codingレッスンでコードを書いて実行できますか？

はい。すべてのVibe Codingレッスンに組み込みコードエディタが含まれているため、ブラウザでリアルコードを書いて実行し、即座のAIフィードバックを取得できます。ローカル設定は不要です。

このコースのすべてのレッスン

  1. 役割と制約
  2. Few-Shot例
  3. 大きなタスクを手順に分解する
  4. 技術とスタイルを指定する
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