Expression Engine

Orchka uses JSONata as its expression language, allowing you to transform and manipulate data as it flows between nodes.

Syntax

Expressions are written inside double curly braces:

{{ expression }}

Accessing Data

Input Data (`$input`)

Access data from the previous node using $input:

{{ $input.propertyName }}

Examples:

{{ $input.user.name }}          // Nested property
{{ $input.items[0] }}           // Array index
{{ $input.items[0].id }}        // Nested array access
{{ $input.response.data.users }} // Deep nesting

Previous Nodes

Access data from any previous node by name:

{{ $nodes.HTTP_Request.data.result }}
{{ $nodes.AI_Agent.response }}

Common Operations

String Operations

{{ $uppercase($input.name) }}              // JOHN
{{ $lowercase($input.name) }}              // john
{{ $trim($input.text) }}                   // Remove whitespace
{{ $substring($input.text, 0, 10) }}       // First 10 chars
{{ $replace($input.text, "old", "new") }}  // Replace text
{{ $input.first & " " & $input.last }}     // Concatenation

Numeric Operations

{{ $input.price * 1.1 }}                   // Multiply
{{ $sum($input.items.price) }}             // Sum array
{{ $average($input.scores) }}              // Average
{{ $round($input.value, 2) }}              // Round to 2 decimals
{{ $floor($input.num) }}                   // Floor
{{ $ceil($input.num) }}                    // Ceiling

Array Operations

{{ $count($input.items) }}                 // Array length
{{ $filter($input.items, function($v) { $v.active = true }) }}
{{ $map($input.items, function($v) { $v.name }) }}
{{ $sort($input.items, function($a, $b) { $a.date > $b.date }) }}
{{ $append($input.arr1, $input.arr2) }}    // Merge arrays
{{ $distinct($input.tags) }}               // Unique values

Conditional Logic

{{ $input.status = "active" ? "Yes" : "No" }}
{{ $exists($input.email) ? $input.email : "N/A" }}
{{ $input.score >= 90 ? "A" : $input.score >= 80 ? "B" : "C" }}

Date & Time

{{ $now() }}                               // Current timestamp
{{ $toMillis($input.date) }}               // To milliseconds
{{ $fromMillis($input.timestamp) }}        // From milliseconds

Object Operations

{{ $keys($input.user) }}                   // Get object keys
{{ $lookup($input.users, "id") }}          // Lookup by key
{{ $merge([$input.defaults, $input.custom]) }} // Merge objects
{{ $spread($input.items) }}                // Spread array to object

Real-World Examples

API Response Transformation

// Input from HTTP Request
{
  "data": {
    "users": [
      { "id": 1, "name": "Alice", "email": "alice@example.com" },
      { "id": 2, "name": "Bob", "email": "bob@example.com" }
    ]
  }
}

Expression to extract names:

{{ $map($input.data.users, function($u) { $u.name }) }}
// Result: ["Alice", "Bob"]

Building API Request Body

{
  "user": "{{ $input.username }}",
  "timestamp": "{{ $now() }}",
  "items": "{{ $filter($input.products, function($p) { $p.inStock = true }) }}"
}

Conditional Message

{{ $input.count > 0 ? "Found " & $string($input.count) & " results" : "No results found" }}

Best Practices

Use descriptive paths - $input.user.profile.name is clearer than $input.a.b.c
Handle missing data - Use $exists() or default values
Test expressions - Use the expression preview in the settings panel
Keep it simple - Break complex transformations into multiple nodes

Debugging

Use the Node Detail Modal to:

View input data from previous nodes
Preview expression results
See the actual output after execution

JSONata Reference

Full JSONata documentation.

Node Types

Configure nodes with expressions.

JSONata Reference

Node Types

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