🔍Project: AI Code Reviewer

Build a tool that reviews code for bugs and improvements

Project: AI Code Reviewer

Build a tool that reads source files and provides code reviews.

What We're Building

A CLI tool that:

Reads a source file
Analyzes it for bugs, security issues, and improvements
Outputs a structured review report

The Code

Create reviewer.js:

JavaScript
import Anthropic from "@anthropic-ai/sdk";
import fs from "fs";
import path from "path";

const client = new Anthropic();

async function reviewCode(filePath) {
  const absolutePath = path.resolve(filePath);

  if (!fs.existsSync(absolutePath)) {
    console.error("File not found:", absolutePath);
    process.exit(1);
  }

  const code = fs.readFileSync(absolutePath, "utf-8");
  const ext = path.extname(filePath).slice(1);

  console.log(`Reviewing ${filePath}...\n`);

  const response = await client.messages.create({
    model: "claude-sonnet-4-6",
    max_tokens: 4000,
    messages: [{
      role: "user",
      content: `Review this ${ext} code for:

1. **Bugs** - Logic errors, off-by-one errors, null/undefined issues
2. **Security** - SQL injection, XSS, input validation
3. **Performance** - Unnecessary loops, missing caching, N+1 queries
4. **Best Practices** - Naming, structure, patterns

For each issue found:
- Severity: 🔴 Critical / 🟡 Warning / 🔵 Info
- Line number (approximate)
- Description
- Suggested fix with code example

If no issues found in a category, say "No issues found."

End with an overall score out of 10 and a summary.

\`\`\`${ext}
${code}
\`\`\``
    }]
  });

  console.log(response.content[0].text);
  console.log(`\nTokens used: ${response.usage.input_tokens} input, ${response.usage.output_tokens} output`);
}

// Get file path from command line
const filePath = process.argv[2];
if (!filePath) {
  console.log("Usage: node reviewer.js <file-path>");
  process.exit(1);
}

reviewCode(filePath);

Usage

Terminal
node reviewer.js src/auth/login.ts
node reviewer.js server.py
node reviewer.js index.html

Sample Output

Reviewing src/auth/login.ts...

## Bug Analysis

🔴 **Critical** (Line ~12)
SQL Injection vulnerability in user query

// Bad const user = db.query("SELECT * FROM users WHERE id = " + userId);

// Fix const user = db.query("SELECT * FROM users WHERE id = $1", [userId]);


🟡 **Warning** (Line ~25)
Missing null check on user object before accessing properties

## Overall Score: 6/10

Summary: The code has a critical SQL injection vulnerability that must
be fixed before deployment. Other issues are minor but should be
addressed in the next refactor cycle.

Extensions to Try

Multiple files — review a whole directory
JSON output — use structured outputs for machine-readable reports
Git integration — automatically review changed files
CI integration — run as part of your build pipeline

Congratulations! You've completed the course roadmap. Keep building, keep learning!

Module 8

4/9

🌍 Project: Multi-Language Translation App

Project: Document Analyzer 📄

4/9