Code Node

Khi built-in nodes không đủ, Code node cho bạn viết JavaScript tùy ý — từ data processing đến API calls phức tạp.

🎯 Mục tiêu bài học

TB5 min

🎯 Mục tiêu

Viết code trong n8n Code node
Xử lý data phức tạp
Call external APIs
Build reusable logic

Checkpoint

Khi nào cần dùng Code node thay vì built-in nodes? Cho ví dụ cụ thể.

Task 0

📖 Code Node Basics

TB5 min

1. Code Node Basics

1.1 Two Modes

Mode	Description	Use Case
Run Once for All Items	Code chạy 1 lần, nhận tất cả items	Aggregation, sorting, complex logic
Run Once for Each Item	Code chạy cho từng item riêng	Transform, validate each item

1.2 Hello World

JavaScript

1// Mode: Run Once for Each Item
2// Input: Each item from previous node
3
4const name = $input.item.json.name;
5const greeting = 'Hello, ' + name + '!';
6
7return {
8  json: {
9    greeting,
10    processedAt: new Date().toISOString()
11  }
12};

1.3 Access Input Data

JavaScript

1// === Run Once for Each Item ===
2const item = $input.item.json;
3// item.name, item.email, item.price...
4
5// === Run Once for All Items ===
6const items = $input.all();
7// items[0].json.name, items[1].json.name...
8
9// Access by node name
10const webhookData = $('Webhook').item.json;
11const sheetsData = $('Google Sheets').all();

1.4 Return Data

JavaScript

1// Return single item
2return {
3  json: { result: "success", value: 42 }
4};
5
6// Return multiple items
7return [
8  { json: { name: "A", score: 95 } },
9  { json: { name: "B", score: 87 } },
10  { json: { name: "C", score: 72 } }
11];
12
13// Return nothing (filter out item)
14return [];

Checkpoint

Phân biệt "Run Once for All Items" và "Run Once for Each Item". Khi nào dùng mode nào?

Task 1

📊 Data Processing

TB5 min

2. Data Processing

2.1 Map & Transform

JavaScript

1// Mode: Run Once for All Items
2const items = $input.all();
3
4const transformed = items.map(item => {
5  const d = item.json;
6  return {
7    json: {
8      fullName: (d.firstName + ' ' + d.lastName).trim(),
9      email: d.email.toLowerCase().trim(),
10      revenue: d.quantity * d.unitPrice,
11      category: categorize(d.revenue),
12      isVIP: d.totalSpend > 10000000
13    }
14  };
15});
16
17function categorize(amount) {
18  if (amount > 5000000) return 'Premium';
19  if (amount > 1000000) return 'Standard';
20  return 'Basic';
21}
22
23return transformed;

2.2 Filter Complex Conditions

JavaScript

1// Mode: Run Once for All Items
2const items = $input.all();
3
4const filtered = items.filter(item => {
5  const d = item.json;
6  const createdDate = new Date(d.createdAt);
7  const thirtyDaysAgo = new Date();
8  thirtyDaysAgo.setDate(thirtyDaysAgo.getDate() - 30);
9  
10  return (
11    d.status === 'active' &&
12    d.amount > 0 &&
13    d.email.includes('@') &&
14    createdDate > thirtyDaysAgo
15  );
16});
17
18return filtered;

2.3 Group By & Aggregate

JavaScript

1// Mode: Run Once for All Items
2const items = $input.all();
3
4// Group by category
5const groups = {};
6for (const item of items) {
7  const cat = item.json.category;
8  if (!groups[cat]) {
9    groups[cat] = { count: 0, totalRevenue: 0, items: [] };
10  }
11  groups[cat].count++;
12  groups[cat].totalRevenue += item.json.revenue;
13  groups[cat].items.push(item.json.name);
14}
15
16// Convert to array of items
17return Object.entries(groups).map(([category, data]) => ({
18  json: {
19    category,
20    count: data.count,
21    totalRevenue: data.totalRevenue,
22    avgRevenue: Math.round(data.totalRevenue / data.count),
23    topItems: data.items.slice(0, 5)
24  }
25}));

2.4 Deduplicate with Priority

JavaScript

1// Keep highest-value duplicate
2const items = $input.all();
3const unique = new Map();
4
5for (const item of items) {
6  const key = item.json.email;
7  const existing = unique.get(key);
8  
9  if (!existing || item.json.value > existing.json.value) {
10    unique.set(key, item);
11  }
12}
13
14return Array.from(unique.values());

Checkpoint

Viết code Group By category và tính tổng revenue. Dùng approach nào?

Task 2

📝 String & Date Processing

TB5 min

3. String & Date Processing

3.1 Vietnamese Text Processing

JavaScript

1// Remove Vietnamese diacritics
2function removeDiacritics(str) {
3  return str.normalize('NFD').replace(/[\u0300-\u036f]/g, '');
4}
5
6// Slug generation
7function toSlug(text) {
8  return removeDiacritics(text)
9    .toLowerCase()
10    .replace(/[^a-z0-9]+/g, '-')
11    .replace(/^-|-$/g, '');
12}
13
14const name = $input.item.json.name; // "Nguyễn Văn Anh"
15return {
16  json: {
17    name,
18    slug: toSlug(name),        // "nguyen-van-anh"
19    search: removeDiacritics(name) // "Nguyen Van Anh"
20  }
21};

3.2 Date Operations

JavaScript

1// Parse & format dates
2const dateStr = $input.item.json.date; // "2026-01-20"
3const date = new Date(dateStr);
4
5const day = date.getDate().toString().padStart(2, '0');
6const month = (date.getMonth() + 1).toString().padStart(2, '0');
7const year = date.getFullYear();
8
9return {
10  json: {
11    original: dateStr,
12    formatted: day + '/' + month + '/' + year,  // "20/01/2026"
13    dayOfWeek: ['CN', 'T2', 'T3', 'T4', 'T5', 'T6', 'T7'][date.getDay()],
14    isWeekend: [0, 6].includes(date.getDay()),
15    daysFromNow: Math.ceil((date - new Date()) / (1000 * 60 * 60 * 24))
16  }
17};

3.3 Parse Unstructured Text

JavaScript

1// Extract info from email body
2const body = $input.item.json.emailBody;
3
4// Extract order number: "Order #12345"
5const orderMatch = body.match(/Order #(\d+)/i);
6const orderId = orderMatch ? orderMatch[1] : null;
7
8// Extract amount: "Total: 1,500,000 VND"
9const amountMatch = body.match(/Total:\s*([\d,]+)\s*VND/i);
10const amount = amountMatch 
11  ? parseInt(amountMatch[1].replace(/,/g, ''))
12  : null;
13
14// Extract email
15const emailMatch = body.match(/[\w.-]+@[\w.-]+\.\w+/);
16const email = emailMatch ? emailMatch[0] : null;
17
18return {
19  json: { orderId, amount, email, rawBody: body }
20};

Checkpoint

Hàm removeDiacritics hoạt động như thế nào? Regex /[\u0300-\u036f]/g match cái gì?

Task 3

🌐 HTTP Requests in Code

TB5 min

4. HTTP Requests in Code

4.1 Fetch API

JavaScript

1// Mode: Run Once for Each Item
2const userId = $input.item.json.userId;
3
4const response = await fetch('https://api.example.com/users/' + userId, {
5  method: 'GET',
6  headers: {
7    'Authorization': 'Bearer ' + $env.API_TOKEN,
8    'Content-Type': 'application/json'
9  }
10});
11
12if (!response.ok) {
13  throw new Error('API error: ' + response.status);
14}
15
16const userData = await response.json();
17
18return {
19  json: {
20    ...($input.item.json),
21    userName: userData.name,
22    userEmail: userData.email
23  }
24};

4.2 POST Request

JavaScript

1const payload = {
2  model: "gpt-4o-mini",
3  messages: [
4    { role: "system", content: "Classify this text as positive/negative/neutral." },
5    { role: "user", content: $input.item.json.text }
6  ],
7  temperature: 0
8};
9
10const response = await fetch('https://api.openai.com/v1/chat/completions', {
11  method: 'POST',
12  headers: {
13    'Authorization': 'Bearer ' + $env.OPENAI_API_KEY,
14    'Content-Type': 'application/json'
15  },
16  body: JSON.stringify(payload)
17});
18
19const data = await response.json();
20const sentiment = data.choices[0].message.content;
21
22return {
23  json: {
24    text: $input.item.json.text,
25    sentiment
26  }
27};

Checkpoint

Cách gọi API bằng fetch() trong Code node? Cần await và xử lý response ra sao?

Task 4

🛡️ Error Handling

TB5 min

5. Error Handling

5.1 Try-Catch

JavaScript

1try {
2  const data = JSON.parse($input.item.json.rawData);
3  const result = processData(data);
4  
5  return {
6    json: { success: true, result }
7  };
8} catch (error) {
9  return {
10    json: {
11      success: false,
12      error: error.message,
13      originalData: $input.item.json.rawData
14    }
15  };
16}

5.2 Validation

JavaScript

1function validate(item) {
2  const errors = [];
3  
4  if (!item.email || !item.email.includes('@'))
5    errors.push('Invalid email');
6  
7  if (!item.name || item.name.length < 2)
8    errors.push('Name too short');
9  
10  if (item.amount && item.amount < 0)
11    errors.push('Negative amount');
12  
13  return errors;
14}
15
16const errors = validate($input.item.json);
17
18if (errors.length > 0) {
19  return {
20    json: {
21      valid: false,
22      errors,
23      original: $input.item.json
24    }
25  };
26}
27
28return {
29  json: {
30    valid: true,
31    ...$input.item.json
32  }
33};

Checkpoint

Try-catch trong Code node quan trọng vì sao? Validation function nên check những gì?

Task 5

🔧 Practical Patterns

TB5 min

6. Practical Patterns

6.1 Build HTML Email

JavaScript

1const items = $input.all();
2
3// Build table rows from data
4const rows = items.map(item => {
5  const name = item.json.name;
6  const amount = item.json.amount.toLocaleString('vi-VN');
7  const status = item.json.status;
8  return '  <tr><td>' + name + '</td><td>' + amount + ' ₫</td><td>' + status + '</td></tr>';
9}).join('\n');
10
11// Build full HTML
12const header = '<h2>Daily Sales Report</h2>';
13const dateStr = new Date().toLocaleDateString('vi-VN');
14const tableStart = '<table border="1" cellpadding="8">';
15const tableHeader = '  <tr><th>Name</th><th>Amount</th><th>Status</th></tr>';
16const tableEnd = '</table>';
17const footer = '<p>Total: ' + items.length + ' orders</p>';
18
19const html = [header, '<p>Date: ' + dateStr + '</p>',
20  tableStart, tableHeader, rows, tableEnd, footer].join('\n');
21
22return [{ json: { html: html, subject: 'Daily Sales Report' } }];

6.2 CSV Generation

JavaScript

1const items = $input.all();
2const headers = Object.keys(items[0].json);
3
4const csv = [
5  headers.join(','),
6  ...items.map(item =>
7    headers.map(h => '"' + (item.json[h] ?? '') + '"').join(',')
8  )
9].join('\n');
10
11return [{ json: { csv, filename: 'report_' + Date.now() + '.csv' } }];

6.3 Rate-Limited Batch Processing

JavaScript

1const items = $input.all();
2const batchSize = 5;
3const delayMs = 1000;
4const results = [];
5
6for (let i = 0; i < items.length; i += batchSize) {
7  const batch = items.slice(i, i + batchSize);
8  
9  const batchResults = await Promise.all(
10    batch.map(item => processItem(item.json))
11  );
12  
13  results.push(...batchResults);
14  
15  if (i + batchSize < items.length) {
16    await new Promise(resolve => setTimeout(resolve, delayMs));
17  }
18}
19
20return results.map(r => ({ json: r }));

7. Hands-on Lab

Lab 1: CSV Parser & Transformer

Webhook — Receive raw CSV text
Code — Parse CSV, clean data, calculate totals
Code — Generate summary (groups, averages, top items)
Slack — Post formatted results

Lab 2: AI-Powered Classifier

Google Sheets — Get unclassified items
Code — Call OpenAI API to classify each item
Code — Aggregate results by classification
Google Sheets — Update with classifications

Lab 3: HTML Report Generator

Schedule (end of day)
HTTP Request — Get day's data from multiple APIs
Code — Build HTML email with tables, charts, KPIs
Email — Send to stakeholders

📝 Quiz

🎯 Key Takeaways

Two modes — "Each Item" for transforms, "All Items" for aggregation
$input — Access current/all items
fetch() — Call any API from code
Return format — Object với key json hoặc array of objects
Error handling — Always try-catch for production workflows

Checkpoint

Viết Code node tạo HTML email report từ danh sách items. Cần return data ở format nào?

Task 6

🚀 Bài tiếp theo

Error Handling & Monitoring — Xử lý lỗi và monitoring production workflows!