n8n JavaScript代码节点使用指南：数据访问、执行模式与最佳实践

n8n-code-javascript by czlonkowski/n8n-skills

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安装命令

npx skills add https://github.com/czlonkowski/n8n-skills --skill n8n-code-javascript

开发数据分析生产力

🇨🇳中文介绍

JavaScript 代码节点

在 n8n 代码节点中编写 JavaScript 代码的专家指南。

快速开始

// Basic template for Code nodes
const items = $input.all();

// Process data
const processed = items.map(item => ({
  json: {
    ...item.json,
    processed: true,
    timestamp: new Date().toISOString()
  }
}));

return processed;

基本规则

选择“对所有项目运行一次”模式（适用于大多数用例）
访问数据：使用 $input.all()、$input.first() 或 $input.item
关键：必须返回 [{json: {...}}] 格式
关键：Webhook 数据位于 $json.body 下（而不是直接位于下）

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对所有项目运行一次（推荐 - 默认）

适用于： 95% 的用例

工作原理：无论输入数量多少，代码仅执行一次
数据访问：$input.all() 或 items 数组
最适合：聚合、过滤、批处理、转换、使用所有数据进行 API 调用
性能：对于多个项目更快（单次执行）

// Example: Calculate total from all items const allItems = $input.all(); const total = allItems.reduce((sum, item) => sum + (item.json.amount || 0), 0);

return [{ json: { total, count: allItems.length, average: total / allItems.length } }];

✅ 跨数据集比较项目
✅ 计算总计、平均值或统计信息
✅ 对项目进行排序或排名
✅ 去重
✅ 构建聚合报告
✅ 合并来自多个项目的数据

对每个项目运行一次

适用于： 仅限特殊情况

工作原理：代码为每个输入项目单独执行
数据访问：$input.item 或 $item
最适合：特定于项目的逻辑、独立操作、每个项目的验证
性能：对于大型数据集较慢（多次执行）

// Example: Add processing timestamp to each item const item = $input.item;

return [{ json: { ...item.json, processed: true, processedAt: new Date().toISOString() } }];

✅ 每个项目需要独立的 API 调用
✅ 具有不同错误处理的每个项目验证
✅ 基于项目属性的特定项目转换
✅ 由于业务逻辑要求必须单独处理项目时

需要查看多个项目？ → 使用“所有项目”模式
每个项目完全独立？ → 使用“每个项目”模式
不确定？ → 使用“所有项目”模式（您始终可以在内部循环）

模式 1：$input.all() - 最常用

适用于：处理数组、批处理操作、聚合

// Get all items from previous node
const allItems = $input.all();

// Filter, map, reduce as needed
const valid = allItems.filter(item => item.json.status === 'active');
const mapped = valid.map(item => ({
  json: {
    id: item.json.id,
    name: item.json.name
  }
}));

return mapped;

模式 2：$input.first() - 非常常用

适用于：处理单个对象、API 响应、先进先出

// Get first item only
const firstItem = $input.first();
const data = firstItem.json;

return [{
  json: {
    result: processData(data),
    processedAt: new Date().toISOString()
  }
}];

模式 3：$input.item - 仅限“每个项目”模式

适用于：在“对每个项目运行一次”模式下

// Current item in loop (Each Item mode only)
const currentItem = $input.item;

return [{
  json: {
    ...currentItem.json,
    itemProcessed: true
  }
}];

模式 4：$node - 引用其他节点

适用于：需要工作流中特定节点的数据

// Get output from specific node
const webhookData = $node["Webhook"].json;
const httpData = $node["HTTP Request"].json;

return [{
  json: {
    combined: {
      webhook: webhookData,
      api: httpData
    }
  }
}];

参见：DATA_ACCESS.md 获取完整指南

关键：Webhook 数据结构

最常见的错误：Webhook 数据嵌套在 .body 下

// ❌ WRONG - Will return undefined
const name = $json.name;
const email = $json.email;

// ✅ CORRECT - Webhook data is under .body
const name = $json.body.name;
const email = $json.body.email;

// Or with $input
const webhookData = $input.first().json.body;
const name = webhookData.name;

原因：Webhook 节点将所有请求数据包装在 body 属性下。这包括 POST 数据、查询参数和 JSON 负载。

参见：DATA_ACCESS.md 获取完整的 webhook 结构详情

关键规则：始终返回包含 json 属性的对象数组

正确的返回格式

// ✅ Single result
return [{
  json: {
    field1: value1,
    field2: value2
  }
}];

// ✅ Multiple results
return [
  {json: {id: 1, data: 'first'}},
  {json: {id: 2, data: 'second'}}
];

// ✅ Transformed array
const transformed = $input.all()
  .filter(item => item.json.valid)
  .map(item => ({
    json: {
      id: item.json.id,
      processed: true
    }
  }));
return transformed;

// ✅ Empty result (when no data to return)
return [];

// ✅ Conditional return
if (shouldProcess) {
  return [{json: processedData}];
} else {
  return [];
}

错误的返回格式

// ❌ WRONG: Object without array wrapper
return {
  json: {field: value}
};

// ❌ WRONG: Array without json wrapper
return [{field: value}];

// ❌ WRONG: Plain string
return "processed";

// ❌ WRONG: Raw data without mapping
return $input.all();  // Missing .map()

// ❌ WRONG: Incomplete structure
return [{data: value}];  // Should be {json: value}

重要性：后续节点期望数组格式。不正确的格式会导致工作流执行失败。

参见：ERROR_PATTERNS.md #3 获取详细的错误解决方案

基于生产工作流，以下是最有用的模式：

1. 多源数据聚合

合并来自多个 API、webhook 或节点的数据

const allItems = $input.all();
const results = [];

for (const item of allItems) {
  const sourceName = item.json.name || 'Unknown';
  // Parse source-specific structure
  if (sourceName === 'API1' && item.json.data) {
    results.push({
      json: {
        title: item.json.data.title,
        source: 'API1'
      }
    });
  }
}

return results;

2. 使用正则表达式过滤

从文本中提取模式、提及或关键词

const pattern = /\b([A-Z]{2,5})\b/g;
const matches = {};

for (const item of $input.all()) {
  const text = item.json.text;
  const found = text.match(pattern);

  if (found) {
    found.forEach(match => {
      matches[match] = (matches[match] || 0) + 1;
    });
  }
}

return [{json: {matches}}];

3. 数据转换与增强

映射字段、标准化格式、添加计算字段

const items = $input.all();

return items.map(item => {
  const data = item.json;
  const nameParts = data.name.split(' ');

  return {
    json: {
      first_name: nameParts[0],
      last_name: nameParts.slice(1).join(' '),
      email: data.email,
      created_at: new Date().toISOString()
    }
  };
});

4. 前 N 项过滤与排名

排序并限制结果

const items = $input.all();

const topItems = items
  .sort((a, b) => (b.json.score || 0) - (a.json.score || 0))
  .slice(0, 10);

return topItems.map(item => ({json: item.json}));

求和、计数、分组数据

const items = $input.all();
const total = items.reduce((sum, item) => sum + (item.json.amount || 0), 0);

return [{
  json: {
    total,
    count: items.length,
    average: total / items.length,
    timestamp: new Date().toISOString()
  }
}];

参见：COMMON_PATTERNS.md 获取 10 个详细的生产模式

错误预防 - 前 5 大错误

#1：空代码或缺少返回（最常见）

// ❌ WRONG: No return statement
const items = $input.all();
// ... processing code ...
// Forgot to return!

// ✅ CORRECT: Always return data
const items = $input.all();
// ... processing ...
return items.map(item => ({json: item.json}));

#2：表达式语法混淆

// ❌ WRONG: Using n8n expression syntax in code
const value = "{{ $json.field }}";

// ✅ CORRECT: Use JavaScript template literals
const value = `${$json.field}`;

// ✅ CORRECT: Direct access
const value = $input.first().json.field;

#3：错误的返回包装器

// ❌ WRONG: Returning object instead of array
return {json: {result: 'success'}};

// ✅ CORRECT: Array wrapper required
return [{json: {result: 'success'}}];

#4：缺少空值检查

// ❌ WRONG: Crashes if field doesn't exist
const value = item.json.user.email;

// ✅ CORRECT: Safe access with optional chaining
const value = item.json?.user?.email || 'no-email@example.com';

// ✅ CORRECT: Guard clause
if (!item.json.user) {
  return [];
}
const value = item.json.user.email;

#5：Webhook 主体嵌套

// ❌ WRONG: Direct access to webhook data
const email = $json.email;

// ✅ CORRECT: Webhook data under .body
const email = $json.body.email;

参见：ERROR_PATTERNS.md 获取全面的错误指南

内置函数与辅助工具

$helpers.httpRequest()

在代码内部发起 HTTP 请求：

const response = await $helpers.httpRequest({
  method: 'GET',
  url: 'https://api.example.com/data',
  headers: {
    'Authorization': 'Bearer token',
    'Content-Type': 'application/json'
  }
});

return [{json: {data: response}}];

日期和时间操作：

// Current time
const now = DateTime.now();

// Format dates
const formatted = now.toFormat('yyyy-MM-dd');
const iso = now.toISO();

// Date arithmetic
const tomorrow = now.plus({days: 1});
const lastWeek = now.minus({weeks: 1});

return [{
  json: {
    today: formatted,
    tomorrow: tomorrow.toFormat('yyyy-MM-dd')
  }
}];

查询 JSON 结构：

const data = $input.first().json;

// Filter array
const adults = $jmespath(data, 'users[?age >= `18`]');

// Extract fields
const names = $jmespath(data, 'users[*].name');

return [{json: {adults, names}}];

参见：BUILTIN_FUNCTIONS.md 获取完整参考

1. 始终验证输入数据

const items = $input.all();

// Check if data exists
if (!items || items.length === 0) {
  return [];
}

// Validate structure
if (!items[0].json) {
  return [{json: {error: 'Invalid input format'}}];
}

// Continue processing...

2. 使用 Try-Catch 进行错误处理

try {
  const response = await $helpers.httpRequest({
    url: 'https://api.example.com/data'
  });

  return [{json: {success: true, data: response}}];
} catch (error) {
  return [{
    json: {
      success: false,
      error: error.message
    }
  }];
}

3. 优先使用数组方法而非循环

// ✅ GOOD: Functional approach
const processed = $input.all()
  .filter(item => item.json.valid)
  .map(item => ({json: {id: item.json.id}}));

// ❌ SLOWER: Manual loop
const processed = [];
for (const item of $input.all()) {
  if (item.json.valid) {
    processed.push({json: {id: item.json.id}});
  }
}

4. 尽早过滤，稍后处理

// ✅ GOOD: Filter first to reduce processing
const processed = $input.all()
  .filter(item => item.json.status === 'active')  // Reduce dataset first
  .map(item => expensiveTransformation(item));  // Then transform

// ❌ WASTEFUL: Transform everything, then filter
const processed = $input.all()
  .map(item => expensiveTransformation(item))  // Wastes CPU
  .filter(item => item.json.status === 'active');

5. 使用描述性的变量名

// ✅ GOOD: Clear intent
const activeUsers = $input.all().filter(item => item.json.active);
const totalRevenue = activeUsers.reduce((sum, user) => sum + user.json.revenue, 0);

// ❌ BAD: Unclear purpose
const a = $input.all().filter(item => item.json.active);
const t = a.reduce((s, u) => s + u.json.revenue, 0);

6. 使用 console.log() 进行调试

// Debug statements appear in browser console
const items = $input.all();
console.log(`Processing ${items.length} items`);

for (const item of items) {
  console.log('Item data:', item.json);
  // Process...
}

return result;

何时使用代码节点

在以下情况下使用代码节点：

✅ 需要多个步骤的复杂转换
✅ 自定义计算或业务逻辑
✅ 递归操作
✅ 具有复杂结构的 API 响应解析
✅ 多步条件判断
✅ 跨项目的数据聚合

在以下情况下考虑使用其他节点：

❌ 简单的字段映射 → 使用 Set 节点
❌ 基本过滤 → 使用 Filter 节点
❌ 简单的条件判断 → 使用 IF 或 Switch 节点
❌ 仅进行 HTTP 请求 → 使用 HTTP Request 节点

代码节点擅长于：需要链接许多简单节点的复杂逻辑

与其他技能的集成

可与以下配合使用：

n8n 表达式语法：

表达式在其他节点中使用 {{ }} 语法
代码节点直接使用 JavaScript（不使用 {{ }}）
何时使用表达式与代码

n8n MCP 工具专家：

如何查找代码节点：search_nodes({query: "code"})
获取配置帮助：get_node_essentials("nodes-base.code")
验证代码：validate_node_operation()

n8n 节点配置：

模式选择（所有项目 vs 每个项目）
语言选择（JavaScript vs Python）
理解属性依赖关系

n8n 工作流模式：

转换步骤中的代码节点
Webhook → 代码 → API 模式
工作流中的错误处理

n8n 验证专家：

验证代码节点配置
处理验证错误
自动修复常见问题

部署代码节点前，请验证：

代码不为空 - 必须包含有意义的逻辑
存在返回语句 - 必须返回对象数组
正确的返回格式 - 每个项目：{json: {...}}
数据访问正确 - 使用 $input.all()、$input.first() 或 $input.item
没有 n8n 表达式 - 使用 JavaScript 模板字面量：${value}
错误处理 - 对空/未定义输入使用保护子句
Webhook 数据 - 如果来自 webhook，通过 .body 访问
模式选择 - 大多数情况下使用“所有项目”模式
性能 - 优先使用 map/filter 而非手动循环
输出一致 - 所有代码路径返回相同的结构

DATA_ACCESS.md - 全面的数据访问模式
COMMON_PATTERNS.md - 10 个经过生产测试的模式
ERROR_PATTERNS.md - 前 5 大错误及解决方案
BUILTIN_FUNCTIONS.md - 完整的内置函数参考

准备好编写 n8n 代码节点中的 JavaScript 了！ 从简单的转换开始，使用错误模式指南避免常见错误，并参考模式库获取生产就绪的示例。

🇺🇸English

JavaScript Code Node

Expert guidance for writing JavaScript code in n8n Code nodes.

Quick Start

// Basic template for Code nodes
const items = $input.all();

// Process data
const processed = items.map(item => ({
  json: {
    ...item.json,
    processed: true,
    timestamp: new Date().toISOString()
  }
}));

return processed;

Essential Rules

Choose "Run Once for All Items" mode (recommended for most use cases)
Access data : $input.all(), $input.first(), or $input.item
CRITICAL : Must return [{json: {...}}] format
CRITICAL : Webhook data is under $json.body (not $json directly)
Built-ins available : $helpers.httpRequest(), DateTime (Luxon), $jmespath()

Mode Selection Guide

The Code node offers two execution modes. Choose based on your use case:

Run Once for All Items (Recommended - Default)

Use this mode for: 95% of use cases

How it works : Code executes once regardless of input count
Data access : $input.all() or items array
Best for : Aggregation, filtering, batch processing, transformations, API calls with all data
Performance : Faster for multiple items (single execution)

// Example: Calculate total from all items const allItems = $input.all(); const total = allItems.reduce((sum, item) => sum + (item.json.amount || 0), 0);

return [{ json: { total, count: allItems.length, average: total / allItems.length } }];

When to use:

✅ Comparing items across the dataset
✅ Calculating totals, averages, or statistics
✅ Sorting or ranking items
✅ Deduplication
✅ Building aggregated reports
✅ Combining data from multiple items

Run Once for Each Item

Use this mode for: Specialized cases only

How it works : Code executes separately for each input item
Data access : $input.item or $item
Best for : Item-specific logic, independent operations, per-item validation
Performance : Slower for large datasets (multiple executions)

// Example: Add processing timestamp to each item const item = $input.item;

return [{ json: { ...item.json, processed: true, processedAt: new Date().toISOString() } }];

When to use:

✅ Each item needs independent API call
✅ Per-item validation with different error handling
✅ Item-specific transformations based on item properties
✅ When items must be processed separately for business logic

Decision Shortcut:

Need to look at multiple items? → Use "All Items" mode
Each item completely independent? → Use "Each Item" mode
Not sure? → Use "All Items" mode (you can always loop inside)

Data Access Patterns

Pattern 1: $input.all() - Most Common

Use when : Processing arrays, batch operations, aggregations

// Get all items from previous node
const allItems = $input.all();

// Filter, map, reduce as needed
const valid = allItems.filter(item => item.json.status === 'active');
const mapped = valid.map(item => ({
  json: {
    id: item.json.id,
    name: item.json.name
  }
}));

return mapped;

Pattern 2: $input.first() - Very Common

Use when : Working with single objects, API responses, first-in-first-out

// Get first item only
const firstItem = $input.first();
const data = firstItem.json;

return [{
  json: {
    result: processData(data),
    processedAt: new Date().toISOString()
  }
}];

Pattern 3: $input.item - Each Item Mode Only

Use when : In "Run Once for Each Item" mode

// Current item in loop (Each Item mode only)
const currentItem = $input.item;

return [{
  json: {
    ...currentItem.json,
    itemProcessed: true
  }
}];

Pattern 4: $node - Reference Other Nodes

Use when : Need data from specific nodes in workflow

// Get output from specific node
const webhookData = $node["Webhook"].json;
const httpData = $node["HTTP Request"].json;

return [{
  json: {
    combined: {
      webhook: webhookData,
      api: httpData
    }
  }
}];

See : DATA_ACCESS.md for comprehensive guide

Critical: Webhook Data Structure

MOST COMMON MISTAKE : Webhook data is nested under .body

// ❌ WRONG - Will return undefined
const name = $json.name;
const email = $json.email;

// ✅ CORRECT - Webhook data is under .body
const name = $json.body.name;
const email = $json.body.email;

// Or with $input
const webhookData = $input.first().json.body;
const name = webhookData.name;

Why : Webhook node wraps all request data under body property. This includes POST data, query parameters, and JSON payloads.

See : DATA_ACCESS.md for full webhook structure details

Return Format Requirements

CRITICAL RULE : Always return array of objects with json property

Correct Return Formats

// ✅ Single result
return [{
  json: {
    field1: value1,
    field2: value2
  }
}];

// ✅ Multiple results
return [
  {json: {id: 1, data: 'first'}},
  {json: {id: 2, data: 'second'}}
];

// ✅ Transformed array
const transformed = $input.all()
  .filter(item => item.json.valid)
  .map(item => ({
    json: {
      id: item.json.id,
      processed: true
    }
  }));
return transformed;

// ✅ Empty result (when no data to return)
return [];

// ✅ Conditional return
if (shouldProcess) {
  return [{json: processedData}];
} else {
  return [];
}

Incorrect Return Formats

// ❌ WRONG: Object without array wrapper
return {
  json: {field: value}
};

// ❌ WRONG: Array without json wrapper
return [{field: value}];

// ❌ WRONG: Plain string
return "processed";

// ❌ WRONG: Raw data without mapping
return $input.all();  // Missing .map()

// ❌ WRONG: Incomplete structure
return [{data: value}];  // Should be {json: value}

Why it matters : Next nodes expect array format. Incorrect format causes workflow execution to fail.

See : ERROR_PATTERNS.md #3 for detailed error solutions

Common Patterns Overview

Based on production workflows, here are the most useful patterns:

1. Multi-Source Data Aggregation

Combine data from multiple APIs, webhooks, or nodes

const allItems = $input.all();
const results = [];

for (const item of allItems) {
  const sourceName = item.json.name || 'Unknown';
  // Parse source-specific structure
  if (sourceName === 'API1' && item.json.data) {
    results.push({
      json: {
        title: item.json.data.title,
        source: 'API1'
      }
    });
  }
}

return results;

2. Filtering with Regex

Extract patterns, mentions, or keywords from text

const pattern = /\b([A-Z]{2,5})\b/g;
const matches = {};

for (const item of $input.all()) {
  const text = item.json.text;
  const found = text.match(pattern);

  if (found) {
    found.forEach(match => {
      matches[match] = (matches[match] || 0) + 1;
    });
  }
}

return [{json: {matches}}];

3. Data Transformation & Enrichment

Map fields, normalize formats, add computed fields

const items = $input.all();

return items.map(item => {
  const data = item.json;
  const nameParts = data.name.split(' ');

  return {
    json: {
      first_name: nameParts[0],
      last_name: nameParts.slice(1).join(' '),
      email: data.email,
      created_at: new Date().toISOString()
    }
  };
});

4. Top N Filtering & Ranking

Sort and limit results

const items = $input.all();

const topItems = items
  .sort((a, b) => (b.json.score || 0) - (a.json.score || 0))
  .slice(0, 10);

return topItems.map(item => ({json: item.json}));

5. Aggregation & Reporting

Sum, count, group data

const items = $input.all();
const total = items.reduce((sum, item) => sum + (item.json.amount || 0), 0);

return [{
  json: {
    total,
    count: items.length,
    average: total / items.length,
    timestamp: new Date().toISOString()
  }
}];

See : COMMON_PATTERNS.md for 10 detailed production patterns

Error Prevention - Top 5 Mistakes

#1: Empty Code or Missing Return (Most Common)

// ❌ WRONG: No return statement
const items = $input.all();
// ... processing code ...
// Forgot to return!

// ✅ CORRECT: Always return data
const items = $input.all();
// ... processing ...
return items.map(item => ({json: item.json}));

#2: Expression Syntax Confusion

// ❌ WRONG: Using n8n expression syntax in code
const value = "{{ $json.field }}";

// ✅ CORRECT: Use JavaScript template literals
const value = `${$json.field}`;

// ✅ CORRECT: Direct access
const value = $input.first().json.field;

#3: Incorrect Return Wrapper

// ❌ WRONG: Returning object instead of array
return {json: {result: 'success'}};

// ✅ CORRECT: Array wrapper required
return [{json: {result: 'success'}}];

#4: Missing Null Checks

// ❌ WRONG: Crashes if field doesn't exist
const value = item.json.user.email;

// ✅ CORRECT: Safe access with optional chaining
const value = item.json?.user?.email || 'no-email@example.com';

// ✅ CORRECT: Guard clause
if (!item.json.user) {
  return [];
}
const value = item.json.user.email;

#5: Webhook Body Nesting

// ❌ WRONG: Direct access to webhook data
const email = $json.email;

// ✅ CORRECT: Webhook data under .body
const email = $json.body.email;

See : ERROR_PATTERNS.md for comprehensive error guide

Built-in Functions & Helpers

$helpers.httpRequest()

Make HTTP requests from within code:

const response = await $helpers.httpRequest({
  method: 'GET',
  url: 'https://api.example.com/data',
  headers: {
    'Authorization': 'Bearer token',
    'Content-Type': 'application/json'
  }
});

return [{json: {data: response}}];

DateTime (Luxon)

Date and time operations:

// Current time
const now = DateTime.now();

// Format dates
const formatted = now.toFormat('yyyy-MM-dd');
const iso = now.toISO();

// Date arithmetic
const tomorrow = now.plus({days: 1});
const lastWeek = now.minus({weeks: 1});

return [{
  json: {
    today: formatted,
    tomorrow: tomorrow.toFormat('yyyy-MM-dd')
  }
}];

$jmespath()

Query JSON structures:

const data = $input.first().json;

// Filter array
const adults = $jmespath(data, 'users[?age >= `18`]');

// Extract fields
const names = $jmespath(data, 'users[*].name');

return [{json: {adults, names}}];

See : BUILTIN_FUNCTIONS.md for complete reference

Best Practices

1. Always Validate Input Data

const items = $input.all();

// Check if data exists
if (!items || items.length === 0) {
  return [];
}

// Validate structure
if (!items[0].json) {
  return [{json: {error: 'Invalid input format'}}];
}

// Continue processing...

2. Use Try-Catch for Error Handling

try {
  const response = await $helpers.httpRequest({
    url: 'https://api.example.com/data'
  });

  return [{json: {success: true, data: response}}];
} catch (error) {
  return [{
    json: {
      success: false,
      error: error.message
    }
  }];
}

3. Prefer Array Methods Over Loops

// ✅ GOOD: Functional approach
const processed = $input.all()
  .filter(item => item.json.valid)
  .map(item => ({json: {id: item.json.id}}));

// ❌ SLOWER: Manual loop
const processed = [];
for (const item of $input.all()) {
  if (item.json.valid) {
    processed.push({json: {id: item.json.id}});
  }
}

4. Filter Early, Process Late

// ✅ GOOD: Filter first to reduce processing
const processed = $input.all()
  .filter(item => item.json.status === 'active')  // Reduce dataset first
  .map(item => expensiveTransformation(item));  // Then transform

// ❌ WASTEFUL: Transform everything, then filter
const processed = $input.all()
  .map(item => expensiveTransformation(item))  // Wastes CPU
  .filter(item => item.json.status === 'active');

5. Use Descriptive Variable Names

// ✅ GOOD: Clear intent
const activeUsers = $input.all().filter(item => item.json.active);
const totalRevenue = activeUsers.reduce((sum, user) => sum + user.json.revenue, 0);

// ❌ BAD: Unclear purpose
const a = $input.all().filter(item => item.json.active);
const t = a.reduce((s, u) => s + u.json.revenue, 0);

6. Debug with console.log()

// Debug statements appear in browser console
const items = $input.all();
console.log(`Processing ${items.length} items`);

for (const item of items) {
  console.log('Item data:', item.json);
  // Process...
}

return result;

When to Use Code Node

Use Code node when:

✅ Complex transformations requiring multiple steps
✅ Custom calculations or business logic
✅ Recursive operations
✅ API response parsing with complex structure
✅ Multi-step conditionals
✅ Data aggregation across items

Consider other nodes when:

❌ Simple field mapping → Use Set node
❌ Basic filtering → Use Filter node
❌ Simple conditionals → Use IF or Switch node
❌ HTTP requests only → Use HTTP Request node

Code node excels at : Complex logic that would require chaining many simple nodes

Integration with Other Skills

Works With:

n8n Expression Syntax :

Expressions use {{ }} syntax in other nodes
Code nodes use JavaScript directly (no {{ }})
When to use expressions vs code

n8n MCP Tools Expert :

How to find Code node: search_nodes({query: "code"})
Get configuration help: get_node_essentials("nodes-base.code")
Validate code: validate_node_operation()

n8n Node Configuration :

Mode selection (All Items vs Each Item)
Language selection (JavaScript vs Python)
Understanding property dependencies

n8n Workflow Patterns :

Code nodes in transformation step
Webhook → Code → API pattern
Error handling in workflows

n8n Validation Expert :

Validate Code node configuration
Handle validation errors
Auto-fix common issues

Quick Reference Checklist

Before deploying Code nodes, verify:

Code is not empty - Must have meaningful logic
Return statement exists - Must return array of objects
Proper return format - Each item: {json: {...}}
Data access correct - Using $input.all(), $input.first(), or $input.item
No n8n expressions - Use JavaScript template literals: ${value}
Error handling - Guard clauses for null/undefined inputs
Webhook data - Access via .body if from webhook
Mode selection - "All Items" for most cases
Performance - Prefer map/filter over manual loops
Output consistent - All code paths return same structure

Additional Resources

Related Files

DATA_ACCESS.md - Comprehensive data access patterns
COMMON_PATTERNS.md - 10 production-tested patterns
ERROR_PATTERNS.md - Top 5 errors and solutions
BUILTIN_FUNCTIONS.md - Complete built-in reference

n8n Documentation

Code Node Guide: https://docs.n8n.io/code/code-node/
Built-in Methods: https://docs.n8n.io/code-examples/methods-variables-reference/
Luxon Documentation: https://moment.github.io/luxon/

Ready to write JavaScript in n8n Code nodes! Start with simple transformations, use the error patterns guide to avoid common mistakes, and reference the pattern library for production-ready examples.

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n8n JavaScript代码节点使用指南：数据访问、执行模式与最佳实践

🇨🇳中文介绍

JavaScript 代码节点

快速开始

基本规则

相关 Skills

模式选择指南

对所有项目运行一次（推荐 - 默认）

对每个项目运行一次

数据访问模式

模式 1：$input.all() - 最常用

模式 2：$input.first() - 非常常用

模式 3：$input.item - 仅限“每个项目”模式

模式 4：$node - 引用其他节点

关键：Webhook 数据结构

返回格式要求

正确的返回格式

错误的返回格式

常见模式概述

1. 多源数据聚合

2. 使用正则表达式过滤

3. 数据转换与增强

4. 前 N 项过滤与排名

5. 聚合与报告

错误预防 - 前 5 大错误

#1：空代码或缺少返回（最常见）

#2：表达式语法混淆

#3：错误的返回包装器

#4：缺少空值检查

#5：Webhook 主体嵌套

内置函数与辅助工具

$helpers.httpRequest()

DateTime (Luxon)

$jmespath()

最佳实践

1. 始终验证输入数据

2. 使用 Try-Catch 进行错误处理

3. 优先使用数组方法而非循环

4. 尽早过滤，稍后处理

5. 使用描述性的变量名

6. 使用 console.log() 进行调试

何时使用代码节点

与其他技能的集成

可与以下配合使用：

快速参考清单

其他资源

相关文件

n8n 文档

🇺🇸English

JavaScript Code Node

Quick Start

Essential Rules

Mode Selection Guide

Run Once for All Items (Recommended - Default)

Run Once for Each Item

Data Access Patterns

Pattern 1: $input.all() - Most Common

Pattern 2: $input.first() - Very Common

Pattern 3: $input.item - Each Item Mode Only

Pattern 4: $node - Reference Other Nodes

Critical: Webhook Data Structure

Return Format Requirements

Correct Return Formats

Incorrect Return Formats

Common Patterns Overview

1. Multi-Source Data Aggregation

2. Filtering with Regex

3. Data Transformation & Enrichment

4. Top N Filtering & Ranking

5. Aggregation & Reporting

Error Prevention - Top 5 Mistakes

#1: Empty Code or Missing Return (Most Common)

#2: Expression Syntax Confusion

#3: Incorrect Return Wrapper

#4: Missing Null Checks

#5: Webhook Body Nesting

Built-in Functions & Helpers

$helpers.httpRequest()

DateTime (Luxon)

$jmespath()