Expressions Overview¶

Expressions allow dynamic values in node parameters using data from previous nodes.

Syntax¶

Expressions use double curly braces:

{{ expression }}

Basic Examples¶

Access JSON Data¶

{{ $json.fieldName }}

String Interpolation¶

Hello, {{ $json.name }}! You have {{ $json.count }} messages.

Mathematical Operations¶

{{ $json.price * $json.quantity }}

Expression Context¶

Every expression has access to:

Variable	Description
`$json`	Current item's JSON data
`$item`	Current item index (0-based)
`$node`	Access other nodes' output
`$input`	Input data helpers
`$env`	Environment variables
`$now`	Current timestamp

Where to Use Expressions¶

Expressions work in most node parameter fields:

{
  "type": "n8n-nodes-base.httpRequest",
  "parameters": {
    "url": "https://api.example.com/users/{{ $json.userId }}",
    "method": "GET"
  }
}

Expression Types¶

Simple Reference¶

Direct field access:

{{ $json.email }}

Nested Access¶

Access nested objects:

{{ $json.user.address.city }}

Array Access¶

Access array elements:

{{ $json.items[0].name }}

Conditional¶

Ternary expressions:

{{ $json.status === "active" ? "Yes" : "No" }}

Function Calls¶

Use built-in functions:

{{ $json.name.toUpperCase() }}

Data Flow Example¶

Node A outputs: { "user": "John", "score": 85 }
     ↓
Node B receives and uses: {{ $json.user }} scored {{ $json.score }}
     ↓
Result: "John scored 85"

Error Handling¶

Undefined Values¶

Use optional chaining:

{{ $json.user?.name ?? "Unknown" }}

Default Values¶

Provide fallbacks:

{{ $json.count || 0 }}

Debugging Expressions¶

Code Node¶

Test expressions in a Code node:

return items.map(item => ({
  json: {
    original: item.json,
    computed: item.json.value * 2
  }
}));

Log Output¶

Log values for debugging:

console.log($json);
return items;

Best Practices¶

Use meaningful field names - Makes expressions readable
Handle missing data - Use defaults and null checks
Keep expressions simple - Complex logic belongs in Code nodes
Test with sample data - Verify before production

Next Steps¶

Variables Reference - All available variables
Functions Reference - Built-in functions