n8n-expression-syntax

Name: n8n-expression-syntax
Author: czlonkowski

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How to install n8n-expression-syntax?

czlonkowski/n8n-skills/n8n-expression-syntax

$npx -y skills add czlonkowski/n8n-skills --skill n8n-expression-syntax

Installs into the current project.

Summary

Validate n8n expression syntax and fix common errors. Use when writing n8n expressions, using {{}} syntax, accessing $json/$node variables, troubleshooting expression errors, mapping data between nodes, or referencing webhook data in workflows. Use this skill whenever configuring

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SKILL.md

1	# n8n Expression Syntax
2
3	Expert guide for writing correct n8n expressions in workflows.
4
5	---
6
7	## Expression Format
8
9	All dynamic content in n8n uses double curly braces:
10
11	```
12	{{expression}}
13	```
14
15	Examples:
16	```
17	✅ {{$json.email}}
18	✅ {{$json.body.name}}
19	✅ {{$node["HTTP Request"].json.data}}
20	❌ $json.email (no braces - treated as literal text)
21	❌ {$json.email} (single braces - invalid)
22	```
23
24	---
25
26	## Core Variables
27
28	### $json - Current Node Output
29
30	Access data from the current node:
31
32	```javascript
33	{{$json.fieldName}}
34	{{$json['field with spaces']}}
35	{{$json.nested.property}}
36	{{$json.items[0].name}}
37	```
38
39	### $node - Reference Other Nodes
40
41	Access data from any previous node:
42
43	```javascript
44	{{$node["Node Name"].json.fieldName}}
45	{{$node["HTTP Request"].json.data}}
46	{{$node["Webhook"].json.body.email}}
47	```
48
49	Important:
50	- Node names must be in quotes
51	- Node names are case-sensitive
52	- Must match exact node name from workflow
53
54	### $now - Current Timestamp
55
56	Access current date/time:
57
58	```javascript
59	{{$now}}
60	{{$now.toFormat('yyyy-MM-dd')}}
61	{{$now.toFormat('HH:mm:ss')}}
62	{{$now.plus({days: 7})}}
63	```
64
65	### $env - Environment Variables
66
67	Access environment variables:
68
69	```javascript
70	{{$env.API_KEY}}
71	{{$env.DATABASE_URL}}
72	```
73
74	Warning: Some n8n instances have `N8N_BLOCK_ENV_ACCESS_IN_NODE` enabled, which blocks `$env` access entirely. If `$env` returns errors, use alternative approaches:
75	- Store values in credentials instead
76	- Use a Set node with manually entered values
77	- Pass values through webhook query parameters
78
79	---
80
81	## 🚨 CRITICAL: Webhook Data Structure
82
83	Most Common Mistake: Webhook data is NOT at the root!
84
85	### Webhook Node Output Structure
86
87	```javascript
88	{
89	"headers": {...},
90	"params": {...},
91	"query": {...},
92	"body": { // ⚠️ USER DATA IS HERE!
93	"name": "John",
94	"email": "john@example.com",
95	"message": "Hello"
96	}
97	}
98	```
99
100	### Correct Webhook Data Access
101
102	```javascript
103	❌ WRONG: {{$json.name}}
104	❌ WRONG: {{$json.email}}
105
106	✅ CORRECT: {{$json.body.name}}
107	✅ CORRECT: {{$json.body.email}}
108	✅ CORRECT: {{$json.body.message}}
109	```
110
111	Why: Webhook node wraps incoming data under `.body` property to preserve headers, params, and query parameters.
112
113	---
114
115	## Common Patterns
116
117	### Access Nested Fields
118
119	```javascript
120	// Simple nesting
121	{{$json.user.email}}
122
123	// Array access
124	{{$json.data[0].name}}
125	{{$json.items[0].id}}
126
127	// Bracket notation for spaces
128	{{$json['field name']}}
129	{{$json['user data']['first name']}}
130	```
131
132	### Reference Other Nodes
133
134	```javascript
135	// Node without spaces
136	{{$node["Set"].json.value}}
137
138	// Node with spaces (common!)
139	{{$node["HTTP Request"].json.data}}
140	{{$node["Respond to Webhook"].json.message}}
141
142	// Webhook node
143	{{$node["Webhook"].json.body.email}}
144	```
145
146	### Combine Variables
147
148	```javascript
149	// Concatenation (automatic)
150	Hello {{$json.body.name}}!
151
152	// In URLs
153	https://api.example.com/users/{{$json.body.user_id}}
154
155	// In object properties
156	{
157	"name": "={{$json.body.name}}",
158	"email": "={{$json.body.email}}"
159	}
160	```
161
162	---
163
164	## When NOT to Use Expressions
165
166	### ❌ Code Nodes
167
168	Code nodes use direct JavaScript access, NOT expressions!
169
170	```javascript
171	// ❌ WRONG in Code node
172	const email = '={{$json.email}}';
173	const name = '{{$json.body.name}}';
174
175	// ✅ CORRECT in Code node
176	const email = $json.email;
177	const name = $json.body.name;
178
179	// Or using Code node API
180	const email = $input.item.json.email;
181	const allItems = $input.all();
182	```
183
184	### ❌ Webhook Paths
185
186	```javascript
187	// ❌ WRONG
188	path: "{{$json.user_id}}/webhook"
189
190	// ✅ CORRECT
191	path: "user-webhook" // Static paths only
192	```
193
194	### ❌ Credential Fields
195
196	```javascript
197	// ❌ WRONG
198	apiKey: "={{$env.API_KEY}}"
199
200	// ✅ CORRECT
201	Use n8n credential system, not expressions
202	```
203
204	---
205
206	## The transform gatekeeper
207
208	Before you add any node — or write any code — to transform data, walk this order and stop at the first that fits:
209
210	1. Expression (`{{ ... }}`) in the consuming field. Property access, method chains (`.map().filter().join()`), ternaries, string building, Luxon date math — if it's "take A, produce B" without intermediate variables, it's an expression. This covers most "just transform this" cases.
211	2. Arrow-function IIFE inside an Edit Fields field. When the logic needs intermediate variables, branching, or comments but still operates on one item, wrap it in an immediately-invoked arrow function right in the field value:
212
213	```
214	={{ (() => {
215	const items = $json.line_items;
216	co

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n8n-expression-syntax

4.6kinstalls983forks

View on GitHub

How to install n8n-expression-syntax?

czlonkowski/n8n-skills/n8n-expression-syntax

$npx -y skills add czlonkowski/n8n-skills --skill n8n-expression-syntax

Installs into the current project.

Summary

Files · 1

View on GitHub

SKILL.md

1	# n8n Expression Syntax
2
3	Expert guide for writing correct n8n expressions in workflows.
4
5	---
6
7	## Expression Format
8
9	All dynamic content in n8n uses double curly braces:
10
11	```
12	{{expression}}
13	```
14
15	Examples:
16	```
17	✅ {{$json.email}}
18	✅ {{$json.body.name}}
19	✅ {{$node["HTTP Request"].json.data}}
20	❌ $json.email (no braces - treated as literal text)
21	❌ {$json.email} (single braces - invalid)
22	```
23
24	---
25
26	## Core Variables
27
28	### $json - Current Node Output
29
30	Access data from the current node:
31
32	```javascript
33	{{$json.fieldName}}
34	{{$json['field with spaces']}}
35	{{$json.nested.property}}
36	{{$json.items[0].name}}
37	```
38
39	### $node - Reference Other Nodes
40
41	Access data from any previous node:
42
43	```javascript
44	{{$node["Node Name"].json.fieldName}}
45	{{$node["HTTP Request"].json.data}}
46	{{$node["Webhook"].json.body.email}}
47	```
48
49	Important:
50	- Node names must be in quotes
51	- Node names are case-sensitive
52	- Must match exact node name from workflow
53
54	### $now - Current Timestamp
55
56	Access current date/time:
57
58	```javascript
59	{{$now}}
60	{{$now.toFormat('yyyy-MM-dd')}}
61	{{$now.toFormat('HH:mm:ss')}}
62	{{$now.plus({days: 7})}}
63	```
64
65	### $env - Environment Variables
66
67	Access environment variables:
68
69	```javascript
70	{{$env.API_KEY}}
71	{{$env.DATABASE_URL}}
72	```
73
74	Warning: Some n8n instances have `N8N_BLOCK_ENV_ACCESS_IN_NODE` enabled, which blocks `$env` access entirely. If `$env` returns errors, use alternative approaches:
75	- Store values in credentials instead
76	- Use a Set node with manually entered values
77	- Pass values through webhook query parameters
78
79	---
80
81	## 🚨 CRITICAL: Webhook Data Structure
82
83	Most Common Mistake: Webhook data is NOT at the root!
84
85	### Webhook Node Output Structure
86
87	```javascript
88	{
89	"headers": {...},
90	"params": {...},
91	"query": {...},
92	"body": { // ⚠️ USER DATA IS HERE!
93	"name": "John",
94	"email": "john@example.com",
95	"message": "Hello"
96	}
97	}
98	```
99
100	### Correct Webhook Data Access
101
102	```javascript
103	❌ WRONG: {{$json.name}}
104	❌ WRONG: {{$json.email}}
105
106	✅ CORRECT: {{$json.body.name}}
107	✅ CORRECT: {{$json.body.email}}
108	✅ CORRECT: {{$json.body.message}}
109	```
110
111	Why: Webhook node wraps incoming data under `.body` property to preserve headers, params, and query parameters.
112
113	---
114
115	## Common Patterns
116
117	### Access Nested Fields
118
119	```javascript
120	// Simple nesting
121	{{$json.user.email}}
122
123	// Array access
124	{{$json.data[0].name}}
125	{{$json.items[0].id}}
126
127	// Bracket notation for spaces
128	{{$json['field name']}}
129	{{$json['user data']['first name']}}
130	```
131
132	### Reference Other Nodes
133
134	```javascript
135	// Node without spaces
136	{{$node["Set"].json.value}}
137
138	// Node with spaces (common!)
139	{{$node["HTTP Request"].json.data}}
140	{{$node["Respond to Webhook"].json.message}}
141
142	// Webhook node
143	{{$node["Webhook"].json.body.email}}
144	```
145
146	### Combine Variables
147
148	```javascript
149	// Concatenation (automatic)
150	Hello {{$json.body.name}}!
151
152	// In URLs
153	https://api.example.com/users/{{$json.body.user_id}}
154
155	// In object properties
156	{
157	"name": "={{$json.body.name}}",
158	"email": "={{$json.body.email}}"
159	}
160	```
161
162	---
163
164	## When NOT to Use Expressions
165
166	### ❌ Code Nodes
167
168	Code nodes use direct JavaScript access, NOT expressions!
169
170	```javascript
171	// ❌ WRONG in Code node
172	const email = '={{$json.email}}';
173	const name = '{{$json.body.name}}';
174
175	// ✅ CORRECT in Code node
176	const email = $json.email;
177	const name = $json.body.name;
178
179	// Or using Code node API
180	const email = $input.item.json.email;
181	const allItems = $input.all();
182	```
183
184	### ❌ Webhook Paths
185
186	```javascript
187	// ❌ WRONG
188	path: "{{$json.user_id}}/webhook"
189
190	// ✅ CORRECT
191	path: "user-webhook" // Static paths only
192	```
193
194	### ❌ Credential Fields
195
196	```javascript
197	// ❌ WRONG
198	apiKey: "={{$env.API_KEY}}"
199
200	// ✅ CORRECT
201	Use n8n credential system, not expressions
202	```
203
204	---
205
206	## The transform gatekeeper
207
208	Before you add any node — or write any code — to transform data, walk this order and stop at the first that fits:
209
210	1. Expression (`{{ ... }}`) in the consuming field. Property access, method chains (`.map().filter().join()`), ternaries, string building, Luxon date math — if it's "take A, produce B" without intermediate variables, it's an expression. This covers most "just transform this" cases.
211	2. Arrow-function IIFE inside an Edit Fields field. When the logic needs intermediate variables, branching, or comments but still operates on one item, wrap it in an immediately-invoked arrow function right in the field value:
212
213	```
214	={{ (() => {
215	const items = $json.line_items;
216	co

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