expression-syntax

name	expression-syntax
description	Expression syntax — variables, methods, JMESPath, data references. This skill should be used when the user asks to write expressions, reference data between nodes, use JMESPath, or debug expression errors.

Expression Syntax

Complete reference for n8n expression syntax — variables, data references, built-in methods, and common patterns.

Expression Basics

Expressions use double curly braces: {{ expression }}. They can reference data from previous nodes, environment variables, and built-in functions.

{{ $json.fieldName }}
{{ $json["field with spaces"] }}
{{ $json.nested.field }}

Built-in Variables

Current Item Data

Variable	Description
$json	Current item's JSON data (alias for $input.item.json)
$binary	Current item's binary data
$input.item.json	Full form of current item
$input.all()	All items from previous node (array)
$input.first()	First item from previous node
$input.last()	Last item from previous node

Node References

Variable	Description
$node["Node Name"].json	Data from a specific named node
$("Node Name").item.json	Same as above (shorthand)
$("Node Name").all()	All items from a specific node
$("Node Name").first()	First item from a specific node

Workflow & Execution

Variable	Description
$workflow.id	Current workflow ID
$workflow.name	Current workflow name
$workflow.active	Whether workflow is active
$execution.id	Current execution ID
$execution.mode	Execution mode (manual, trigger, webhook)
$execution.resumeUrl	URL to resume a waiting execution

Environment & Parameters

Variable	Description
$env.VARIABLE_NAME	Environment variable
$vars.variableName	n8n workflow variable
$parameter.fieldName	Current node parameter value
$itemIndex	Index of current item in the array
$runIndex	Current run index (for loops)
$now	Current DateTime
$today	Today's date at midnight

Trigger Data

Variable	Description
$webhookData	Data from webhook trigger
$execution.customData	Custom data set during execution

String Methods

{{ $json.name.toUpperCase() }}
{{ $json.name.toLowerCase() }}
{{ $json.email.includes("@gmail.com") }}
{{ $json.text.replace("old", "new") }}
{{ $json.text.replaceAll("old", "new") }}
{{ $json.name.trim() }}
{{ $json.name.length }}
{{ $json.text.slice(0, 100) }}
{{ $json.text.split(",") }}
{{ $json.name.startsWith("Mr") }}
{{ $json.name.endsWith("Jr") }}

Number Methods

{{ $json.price.toFixed(2) }}
{{ Math.round($json.value) }}
{{ Math.floor($json.value) }}
{{ Math.ceil($json.value) }}
{{ Math.max($json.a, $json.b) }}
{{ Math.min($json.a, $json.b) }}
{{ parseInt($json.stringNumber) }}
{{ parseFloat($json.stringDecimal) }}

Array Methods

{{ $json.items.length }}
{{ $json.items.filter(item => item.status === "active") }}
{{ $json.items.map(item => item.name) }}
{{ $json.items.find(item => item.id === 123) }}
{{ $json.items.some(item => item.price > 100) }}
{{ $json.items.every(item => item.active) }}
{{ $json.tags.join(", ") }}
{{ $json.items.sort((a, b) => a.price - b.price) }}
{{ $json.items.reduce((sum, item) => sum + item.price, 0) }}
{{ $json.items.includes("value") }}

Date and Time

Using Luxon (built-in)

{{ $now.toISO() }}                          // 2024-01-15T10:30:00.000Z
{{ $now.toFormat("yyyy-MM-dd") }}           // 2024-01-15
{{ $now.toFormat("dd/MM/yyyy HH:mm") }}     // 15/01/2024 10:30
{{ $now.plus({ days: 7 }).toISO() }}        // 7 days from now
{{ $now.minus({ hours: 2 }).toISO() }}      // 2 hours ago
{{ $now.startOf("day").toISO() }}           // Start of today
{{ $now.endOf("month").toISO() }}           // End of current month
{{ $now.weekday }}                           // Day of week (1=Mon, 7=Sun)
{{ $now.year }}                              // Current year
{{ $now.month }}                             // Current month (1-12)
{{ $now.day }}                               // Current day of month

Parsing Dates

{{ DateTime.fromISO($json.date) }}
{{ DateTime.fromFormat($json.date, "dd/MM/yyyy") }}
{{ DateTime.fromMillis($json.timestamp) }}
{{ DateTime.fromSeconds($json.unixTimestamp) }}

Date Comparisons

{{ DateTime.fromISO($json.dueDate) < $now }}     // Is past due?
{{ DateTime.fromISO($json.dueDate).diff($now, "days").days }}  // Days until due

JMESPath Expressions

n8n supports JMESPath for complex data queries in the JMESPath expression mode:

// Select nested field
people[*].name

// Filter array
people[?age > `30`]

// Sort
sort_by(people, &name)

// Select multiple fields
people[*].{name: name, email: email}

// Flatten nested arrays
orders[*].items[]

// Conditions
people[?status == 'active'].name

Common Patterns

Conditional Values (Ternary)

{{ $json.status === "active" ? "Yes" : "No" }}
{{ $json.price > 100 ? "Premium" : "Standard" }}
{{ $json.email ? $json.email : "[e-mail]" }}

Null/Undefined Handling

{{ $json.field ?? "default value" }}          // Nullish coalescing
{{ $json.nested?.field ?? "missing" }}        // Optional chaining
{{ $json.items?.length ?? 0 }}               // Safe array length

String Templates

{{ `Hello ${$json.firstName} ${$json.lastName}` }}
{{ `Order #${$json.id} - Total: $${$json.total.toFixed(2)}` }}

Object Manipulation

{{ Object.keys($json) }}                     // Get all field names
{{ Object.values($json) }}                   // Get all values
{{ Object.entries($json) }}                  // Get key-value pairs
{{ JSON.stringify($json.data) }}             // Serialize to string
{{ JSON.parse($json.jsonString) }}           // Parse JSON string

Combine Data from Multiple Nodes

{{ $("HTTP Request").first().json.apiData }}
{{ $("Customers DB").all().map(i => i.json.email) }}
{{ $("Config").first().json.setting ?? "default" }}

Common Mistakes and Fixes

Mistake	Fix
{{ $json.field name }}	{{ $json["field name"] }} — use brackets for spaces
{{ $json.items[0] }} in empty array	{{ $json.items?.[0] ?? null }} — check for empty
{{ $node.NodeName.json }}	{{ $("Node Name").item.json }} — use function syntax
{{ $json.date + 1 }} for adding days	{{ DateTime.fromISO($json.date).plus({days:1}).toISO() }}
{{ $json.price * 1.1 }} returns string	{{ Number($json.price) * 1.1 }} — ensure numeric
Accessing data from parallel branch	Use $("Node Name") to reference specific node by name

Expression Modes

n8n supports two expression modes in different contexts:

1. JavaScript — default for most fields, uses {{ }} syntax
2. JMESPath — available in specific nodes, for complex data querying