Basic Commands

What you'll learn in this chapter: frequently used prompt patterns for file operations, code analysis, debugging, and Git integration

Prerequisites

You should have completed First Run and be comfortable with the basic interface.

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Principles of Effective Prompts

How to give Claude Code instructions that work well:

✅ Good: "Read src/auth/login.js and explain the password hashing logic"
✅ Good: "Look at the README in the current directory and add the missing installation steps"
❌ Bad: "Fix the code" (too vague)
❌ Bad: "Write good code" (no criteria)

The key combination is a specific file name + a clear task + the result you want.

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1. Reading and Analyzing Files

Understanding File Contents

> Read utils/helpers.js and explain what each function does
> Analyze the Props types in src/components/Button.tsx
> Find hardcoded values in config/database.js that should be moved to environment variables

Understanding a Whole Project

> Look at this project's folder structure and explain the overall architecture
> Look at package.json and tell me what tech stack this project uses
> Read README.md and summarize the key points

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2. Writing Code

Creating New Files

> Create a file called utils/validation.js.
  Include validation functions for email, phone number, and password (8+ characters, must include a special character).

> Create components/Modal.jsx.
  props: isOpen, onClose, title, children
  Style it with Tailwind CSS

Adding Features to Existing Code

> Add a user search feature to UserService.js.
  Search by name or email, case-insensitive.

> Add pagination parameters to api/routes/products.js.
  Use the format ?page=1&limit=20.

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3. Debugging

Analyzing and Fixing Errors

> Run npm run build, check for errors, and fix them
> I got this error in the terminal: [paste the error message] — explain the cause and how to fix it
> Run all the tests in the tests/ folder and fix the failing ones

Performance Issues

> The UserList component seems to re-render too often. Find the cause and optimize it
> This SQL query is slow: [paste the query] — suggest ways to optimize it

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4. Refactoring

Improving Code Quality

> utils.js is too big. Split it into separate files by feature
> Refactor this function to be more readable, keeping the behavior identical
> Convert the Promise-based code to async/await

Unifying Code Style

> Update the entire controllers/ folder to match the project's .eslintrc rules
> Replace var with const/let across all components

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5. Writing Tests

> Write Jest unit tests for each function in UserService.js
> Check the current test coverage and add tests for missing edge cases
> E2E test: write the login → dashboard navigation → logout flow with Playwright

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6. Documentation

> Add JSDoc comments to all public functions
> Read the list of API endpoints and add an API documentation section to the README
> Update CHANGELOG.md based on the recent commit messages

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7. Git Operations

Claude Code can run git commands too:

> Check git status and summarize the modified files
> Review the changes, write an appropriate commit message, and commit
> Analyze the diff between the current branch and main, and draft a PR description

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Frequently Used Slash Commands

/model                    # Check the current model
/model claude-opus-4-6    # Switch to Opus (complex tasks)
/model claude-haiku-4-5-20251001  # Switch to Haiku (fast tasks)

/cost                     # This session's cost
/clear                    # Reset the conversation (start with fresh context)
/status                   # Check current settings
/help                     # Full help

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Real-World Workflow Examples

"Add a Feature" Workflow

1. > Get familiar with this project's structure (understand)
2. > Plan how to implement a user profile editing feature (plan)
3. > Implement it according to the plan (execute)
4. > Write tests (verify)
5. > Commit the changes (wrap up)

"Fix a Bug" Workflow

1. > Run npm test and show me the failing tests
2. > Analyze [the failing test file] and find the cause
3. > Fix it
4. > Run npm test again to confirm

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Key Takeaways

• A specific file name + a clear task is the effective combination
• Work in stages: read files → analyze → modify → verify
• Pick the right model for the job with /model (cost optimization)
• Claude Code can run terminal commands directly — git, npm, python, and more

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Level 1 Complete!

Congratulations! You've finished all of Level 1 — Getting Started.