Vibe Coding · 课时

角色与约束

设定人工智能的角色和边界，以获得更好的输出。

第 1 / 4 课13 个步骤

角色与约束 是 CoddyKit 上的免费 Vibe Coding 课时。这是第 1 节课，共 4 节。你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。这是 Vibe Coding 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Vibe Coding 课程共包含 4 节课。

本课时的部分内容尚未翻译，以英文显示。

Tell the AI Who to Be

You already know how to ask AI for code. Now let's get production-quality output on the first try. The fastest upgrade? Give the AI a role and a set of constraints.

A role tells the AI what kind of expert to channel. Constraints tell it the rules it must not break. Together they turn a vague request into a precise brief — the same way a good client gets better work from a freelancer.

What Is a Role?

A role is a one-line identity you assign at the start of a prompt: "You are a senior React engineer" or "Act as a security-focused backend developer."

This isn't magic — it steers the model toward the patterns, vocabulary and standards that kind of person would use. A "senior engineer" writes cleaner, safer code than an unspecified assistant. Tools like Cursor and Claude Code respond strongly to roles because they shape the whole answer.

You are a senior front-end engineer who writes clean, accessible, well-commented JavaScript. Build a function that validates an email address and returns true or false.

Why Roles Improve Output

Without a role, AI gives you the average of everything it has seen — including beginner code from tutorials. With a role, you pull from the expert slice.

Better defaults — a "senior" picks safer patterns.
Right vocabulary — it explains things at your level.
Consistent style — it stays in character across edits.

Think of it as choosing which teammate shows up to help you.

What Is a Constraint?

A constraint is a hard rule the answer must obey. Roles set the vibe; constraints set the boundaries.

Examples of useful constraints:

"Use only vanilla JavaScript — no libraries."
"Keep the function under 20 lines."
"Do not use any external API."
"Return only the code, no explanation."

Each constraint removes a whole category of unwanted answers.

You are a senior JavaScript developer. Constraints: vanilla JS only, no libraries, under 20 lines, include a one-line comment above the function. Write a function that formats a number as US currency.

Roles + Constraints Together

The real power comes from combining them. The role decides how the code is written; the constraints decide what's allowed. Stack them at the top of your prompt so the AI reads the rules before the task.

A reliable template:

Role: who the AI is
Constraints: the must/never list
Task: what to build

ROLE: You are a senior front-end engineer focused on accessibility.
CONSTRAINTS:
- Vanilla JavaScript and HTML only
- No external libraries
- All interactive elements must be keyboard-usable
TASK: Build a button that copies the page URL to the clipboard and shows a 'Copied!' message for 2 seconds.

A Constraint in Action

Here's the kind of clean, self-contained JavaScript a well-constrained prompt produces. Notice it's small, readable, and does exactly one job — because the constraints asked for exactly that.

Run it to see the output.

// Format a number as US currency
function toUSD(amount) {
  return new Intl.NumberFormat('en-US', {
    style: 'currency',
    currency: 'USD'
  }).format(amount);
}

console.log(toUSD(1999.5));
console.log(toUSD(42));

Negative Constraints: The 'Never' List

Some of the most powerful constraints are things you forbid. AI loves to over-deliver — adding libraries, extra features, or rewriting your whole file. A never list reins it in.

"Never add new dependencies."
"Never change files I didn't mention."
"Never use TypeScript — plain JavaScript only."

In agentic tools like Claude Code, a clear never list prevents surprise edits across your project.

You are a careful engineer working in an existing project.
NEVER:
- Add new npm packages
- Edit any file other than cart.js
- Remove existing comments
TASK: In cart.js, add a function getTotal(items) that sums item.price for all items.

Scope Constraints

One constraint beginners forget: limiting scope. Without it, ask for one feature and AI may refactor everything. Pin it down:

"Only modify the function I paste below."
"Give me just the changed lines."
"Don't touch the styling."

Tight scope makes AI output easier to review and far less likely to break working code.

Here is my working function. Change ONLY the sort order to descending. Do not rename anything, do not add features, return only the updated function.

function topScores(scores) {
  return scores.sort((a, b) => a - b).slice(0, 3);
}

Output-Format Constraints

You can also constrain the shape of the reply. This keeps answers easy to paste and use:

"Return only a single code block, no prose."
"Reply with the full file, ready to save."
"List 3 options as a numbered list, code only."

App builders like v0 and Bolt already format output as runnable apps — but inside an editor, saying how you want the answer saves you cleanup time.

You are a JS engineer. Return ONLY the complete function in one code block, with no explanation before or after.

Task: Write debounce(fn, delay) that returns a debounced version of fn.

Build a Reusable Role Header

Pros don't retype roles and constraints every time. They save a role header and reuse it. In Cursor you can store it in a .cursorrules file; in Claude Code, a CLAUDE.md; or just keep a note you paste in.

A good standing header sets your stack, your style, and your never list once — so every prompt inherits it automatically.

PROJECT RULES (paste once, applies to all prompts):
Role: Senior JavaScript engineer who writes clean, commented, accessible code.
Stack: Vanilla JS + HTML/CSS, no frameworks.
Never: add dependencies, use TypeScript, or edit unrelated files.
Style: short functions, descriptive names, no clever one-liners.

Don't Over-Constrain

Constraints are powerful, but too many can box the AI into bad code. If you forbid everything, it can't find a good solution.

Balance:

Constrain things you care about (stack, scope, safety).
Leave room for the AI to choose implementation details.

If output feels stiff or wrong, loosen one constraint and re-run. Aim for a clear brief, not a straitjacket.

Quick Check

You want AI to fix one function without rewriting your whole file. Which addition to your prompt best achieves this?

在交互式课程中回答

Recap: Direct the AI

You learned to steer AI like a director:

Roles pull expert-level output instead of average answers.
Constraints set hard rules: stack, scope, never-lists and output format.
Combine them with a Role → Constraints → Task structure.
Save a reusable role header (.cursorrules / CLAUDE.md).
Don't over-constrain — leave room for good solutions.

Next up: showing the AI examples so it copies the exact style you want.

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常见问题解答

「角色与约束」课时是免费的吗？

是的 — 「角色与约束」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Vibe Coding 课程的其余内容，请升级到 CoddyKit PRO。 Vibe Coding 课程共包含 4 节课。

「角色与约束」这节课中我会学到什么？

设定人工智能的角色和边界，以获得更好的输出。你通过在浏览器中直接运行的动手代码来练习 Vibe Coding，全天候 AI 导师会在你学习这节课的过程中回答你的问题。

学习 Vibe Coding 需要有经验吗？

无需任何先前经验。CoddyKit 上的 Vibe Coding 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。这是第 1 节课，共 4 节。

「角色与约束」课时需要多长时间？

大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。

我能在这节 Vibe Coding 课中编写并运行代码吗？

能。每节 Vibe Coding 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。

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