Reading and Understanding Code

Navigate unfamiliar codebases with AI assistance

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Overview

Reading code is a critical skill. Whether you're exploring open source, onboarding to a new project, or understanding devfoundry examples, AI can accelerate your comprehension.

This template is for:

• Understanding what code does
• Learning how systems are structured
• Decoding unfamiliar syntax or patterns
• Building mental models of existing code

Key insight: Ask specific questions. "Explain this code" is less effective than "What does this function return and when is it called?"

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The Code Reading Template

**Context**: [What project/example this is from]

**My Goal**: [Why I'm reading this code]

**What I Understand**: [Parts I already get]

**What I Don't Understand**: [Specific confusions]

**Code**:
[Paste the code]

**Questions**:
1. [Specific question 1]
2. [Specific question 2]
3. [Specific question 3]

Please explain in beginner-friendly terms.

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Template Deep Dive

Section 1: Context

Purpose: Help AI calibrate explanations

What to include:

• Project or example name
• Where the code is from (file path)
• Tech stack if relevant

Example:

**Context**:
This is from the devfoundry lemonade stand SPA example.
File: src/components/OrderForm.tsx
Tech: React with TypeScript

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Section 2: My Goal

Purpose: Focus the explanation

Different goals get different explanations:

Goal	AI Focus
"Understand the logic"	Step-by-step walkthrough
"Learn this pattern"	Pattern explanation + when to use
"Modify this code"	Entry points and dependencies
"Debug an issue"	Data flow and state changes

Example:

**My Goal**:
I want to understand how form validation works so I can add my own validation rules.

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Section 3: What I Understand

Purpose: Avoid redundant explanations

Example:

**What I Understand**:
- This is a React component that renders a form
- useState creates state variables
- The form has onSubmit handler

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Section 4: What I Don't Understand

Purpose: Focus on your actual confusion

Good examples:

• "What does the ... spread operator do here?"
• "Why is there a function inside the useState call?"
• "When does useEffect run?"

Bad examples:

• "I don't understand anything"
• "This is confusing"

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Section 5: Specific Questions

Purpose: Get targeted answers

Question types:

• What: "What does this line do?"
• Why: "Why is this structured this way?"
• When: "When does this function get called?"
• How: "How does data flow through this?"
• What if: "What happens if I change X?"

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Complete Example

Scenario: Understanding a React Hook

**Context**:
devfoundry lemonade SPA, file: src/hooks/useOrders.ts
This is a custom React hook.

**My Goal**:
Understand how custom hooks work so I can create my own.

**What I Understand**:
- Hooks are functions that start with "use"
- useState and useEffect are built-in hooks
- This hook is being used in App.tsx

**What I Don't Understand**:
- Why is state defined inside this function?
- How does the component using this hook get the data?
- What does "returning an object" mean for the hook?

**Code**:
```typescript
import { useState, useEffect } from 'react';
import { Order } from '../types';

export function useOrders() {
  const [orders, setOrders] = useState<Order[]>([]);
  const [total, setTotal] = useState<number>(0);

  useEffect(() => {
    const newTotal = orders.reduce(
      (sum, order) => sum + order.price * order.quantity,
      0
    );
    setTotal(newTotal);
  }, [orders]);

  const addOrder = (order: Order) => {
    setOrders(prev => [...prev, order]);
  };

  const removeOrder = (id: string) => {
    setOrders(prev => prev.filter(order => order.id !== id));
  };

  return { orders, total, addOrder, removeOrder };
}

Questions:

1. Why are orders and total inside the hook and not in the component?
2. What does return { orders, total, addOrder, removeOrder } do?
3. When a component uses this hook, does it get its own copy of the state?
4. What does [orders] at the end of useEffect mean?

Please explain in beginner-friendly terms with analogies if helpful.

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## Quick Reading Prompts

### Single Line Explanation

What does this line do?

const [count, setCount] = useState(0);

Explain what each part means.

### Function Purpose

What does this function do?

[PASTE FUNCTION]

In one sentence, describe:

1. What it takes as input
2. What it does
3. What it returns

### Pattern Recognition

What pattern is this code using?

[PASTE CODE]

Is this a common pattern? What is it called? When should I use it?

### Data Flow

Trace the data flow in this code:

[PASTE CODE]

Starting from [INPUT], show me step-by-step how data flows through to [OUTPUT].

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## Reading Strategies

### Strategy 1: Top-Down

**Start with the big picture**:

This is a [FILE/MODULE] from [PROJECT].

Before I read the details, please give me:

1. One sentence: What is the purpose of this file?
2. What are the main functions/components?
3. How does it fit into the larger system?

[PASTE CODE or just file path if AI has access]

### Strategy 2: Bottom-Up

**Start with specific confusion**:

I'm reading [FILE] and I don't understand this part:

[PASTE SPECIFIC SECTION]

What does this do? Then explain how it connects to the rest of the file.

### Strategy 3: Trace Execution

**Follow the code path**:

In this code:

[PASTE CODE]

Walk me through what happens when:

1. User clicks the submit button
2. What functions are called (in order)
3. How state changes
4. What the user sees

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## Understanding Different Code Types

### React Components

Code: [PASTE COMPONENT]

Questions:

1. What props does this component accept?
2. What state does it manage?
3. What does it render?
4. What events does it handle?

### API Routes

Code: [PASTE ROUTE HANDLER]

Questions:

1. What HTTP method and path does this handle?
2. What data does it expect in the request?
3. What does it return?
4. What errors can occur?

### Utility Functions

Code: [PASTE FUNCTION]

Questions:

1. What are the inputs (parameters)?
2. What is the output (return value)?
3. What transformation happens?
4. Any edge cases I should know about?

### Configuration Files

Code: [PASTE CONFIG]

Questions:

1. What is this configuring?
2. What do the key settings mean?
3. Which settings are important to change?
4. Which should I leave alone?

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## Building Mental Models

### Request: Diagram Generation

I'm reading this code:

[PASTE CODE]

Please create a Mermaid diagram showing:

• The main components/functions
• How they connect to each other
• The data flow direction

### Request: Analogy

I'm trying to understand:

[PASTE CODE or CONCEPT]

Can you explain this using a real-world analogy? Something like a restaurant, library, or post office would help.

### Request: Simplified Version

This code is complex:

[PASTE CODE]

Can you show me a simplified version that does the same thing? Then explain what the extra complexity in the original adds.

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## Navigating Larger Codebases

### Finding Entry Points

I'm exploring [PROJECT/REPO].

Where should I start reading to understand:

1. How the app starts up?
2. Where the main logic lives?
3. How data flows through the system?

Key files I see: [LIST MAIN FILES]

### Understanding Architecture

This project has these directories: [LIST DIRECTORY STRUCTURE]

Can you explain:

1. What each directory is likely for?
2. Which directories have the core logic?
3. Which are supporting (config, tests, utils)?

### Following Imports

This file imports from several places:

import { useState } from 'react';
import { Order } from '../types';
import { calculateTotal } from '../utils/pricing';
import { useOrders } from '../hooks/useOrders';

What does each import bring in? Which are library imports vs local files?

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## Common Confusing Patterns

### Destructuring

I don't understand this syntax:

const { name, age, ...rest } = person;

What does each part do? What is ...rest?

### Arrow Functions

What's the difference between these:

function add(a, b) { return a + b; }
const add = (a, b) => a + b;
const add = (a, b) => { return a + b; };

When should I use each form?

### Async/Await

I'm confused by async code:

async function fetchData() {
  const response = await fetch('/api/data');
  const data = await response.json();
  return data;
}

What does async do? What does await do? What happens if I remove await?

### Callbacks and Closures

I don't understand why this works:

function createCounter() {
  let count = 0;
  return function() {
    count += 1;
    return count;
  };
}

How does the inner function access count? What is a closure?

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## Checklist: Before Asking AI to Explain Code

- [ ] Stated what project/file the code is from
- [ ] Explained your goal (why you're reading this)
- [ ] Mentioned what you already understand
- [ ] Listed specific confusions
- [ ] Pasted the relevant code
- [ ] Asked specific questions (not just "explain this")

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## Related Templates

- [Getting Started](getting-started) — First steps with AI assistants
- [Debugging](debugging) — When code you're reading has bugs
- [Designing Features](designing-features) — After understanding, planning new features

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## Summary

**Effective code reading prompts**:

1. ✓ Provide context (project, file, tech)
2. ✓ State your goal (why you're reading)
3. ✓ Share what you understand already
4. ✓ Identify specific confusions
5. ✓ Ask targeted questions
6. ✓ Request appropriate format (explanation, diagram, analogy)

**Remember**: Reading code is a skill that improves with practice. Use AI to accelerate learning, but also spend time reading without help to build pattern recognition.

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**Found confusing code?** Use the template above to get clarity!