metabuilder/workflow/plugins/utility/set-variable

Set Variable Node Plugin

Set workflow variables for use in subsequent nodes.

Installation

npm install @metabuilder/workflow-plugin-set-variable

Usage

{
  "id": "set-vars",
  "type": "operation",
  "nodeType": "set-variable",
  "parameters": {
    "variables": {
      "userId": "{{ $json.id }}",
      "userEmail": "{{ $json.email }}",
      "processDate": "{{ new Date().toISOString() }}"
    },
    "mode": "merge"
  }
}

Operations

Set Simple Variables

Store string and number values:

{
  "variables": {
    "count": 0,
    "name": "John Doe",
    "active": true
  }
}

Set Variables from Input Data

Reference input data with template expressions:

{
  "variables": {
    "userId": "{{ $json.id }}",
    "userName": "{{ $json.name }}",
    "userStatus": "{{ $json.status }}"
  }
}

Set Computed Variables

Use expressions to compute values:

{
  "variables": {
    "fullName": "{{ $json.firstName + ' ' + $json.lastName }}",
    "isActive": "{{ $json.status === 'active' }}",
    "count": "{{ $json.items.length }}"
  }
}

Set Complex Variables

Store objects and arrays:

{
  "variables": {
    "userData": {
      "id": "{{ $json.id }}",
      "name": "{{ $json.name }}",
      "email": "{{ $json.email }}"
    },
    "tags": ["{{ $json.tag1 }}", "{{ $json.tag2 }}"]
  }
}

Merge vs Replace Mode

Merge adds to existing variables (default):

{
  "variables": { "newVar": "value" },
  "mode": "merge"
}

Replace clears all previous variables:

{
  "variables": { "var1": "value" },
  "mode": "replace"
}

Parameters

• variables (required): Object with variable definitions
  • Keys must be valid variable names (alphanumeric + underscore)
  • Values can be strings, numbers, booleans, objects, or arrays
  • Supports template expressions in strings
  • Recursively interpolates nested objects
• mode (optional): How to handle existing variables
  • merge (default): Add new variables to existing set
  • replace: Clear existing variables first
  • append: Append to existing array variables

Variable Names

Valid variable names:

• Must start with letter (a-z, A-Z) or underscore (_)
• Can contain letters, numbers (0-9), and underscores
• Are case-sensitive
• Examples: userId, _private, tempData123

Invalid variable names:

• 123var (starts with number)
• user-id (contains hyphen)
• user.id (contains dot)
• user@id (contains special char)

Template Expressions

Variable values support template interpolation:

• {{ $json.fieldName }} - Access input field
• {{ $json.field1 + $json.field2 }} - Concatenate/add
• {{ $json.price * 1.1 }} - Calculate
• {{ $json.items.length }} - Array length
• {{ $json.active ? 'yes' : 'no' }} - Conditionals
• {{ new Date().toISOString() }} - Current timestamp
• {{ $env.API_KEY }} - Environment variables
• {{ $context.tenantId }} - Context values

Reserved Names

These names conflict with built-in variables and should be avoided:

• context
• state
• json
• env
• utils
• $json
• $context
• $state
• $env

Using reserved names will trigger a validation warning.

Features

• Template expression interpolation in variable values
• Nested object and array support
• Multiple variable setting in single node
• Mode selection (merge/replace/append)
• Variable name validation
• Reserved name detection
• Type preservation (strings, numbers, booleans, objects)
• Recursive object interpolation

Examples

Set User Information

{
  "id": "set-user-vars",
  "nodeType": "set-variable",
  "parameters": {
    "variables": {
      "userId": "{{ $json.id }}",
      "userName": "{{ $json.name }}",
      "userEmail": "{{ $json.email }}",
      "isAdmin": "{{ $json.role === 'admin' }}"
    }
  }
}

Set Computed Values

{
  "id": "set-computed",
  "nodeType": "set-variable",
  "parameters": {
    "variables": {
      "total": "{{ $json.subtotal + $json.tax }}",
      "discount": "{{ $json.total * 0.1 }}",
      "finalPrice": "{{ ($json.subtotal + $json.tax) - ($json.total * 0.1) }}",
      "timestamp": "{{ new Date().toISOString() }}"
    }
  }
}

Set Conditional Variables

{
  "id": "set-conditional",
  "nodeType": "set-variable",
  "parameters": {
    "variables": {
      "status": "{{ $json.amount > 1000 ? 'high' : 'normal' }}",
      "requiresApproval": "{{ $json.amount > 5000 }}",
      "priority": "{{ $json.urgent ? 1 : 3 }}"
    }
  }
}

Set Complex Data Structure

{
  "id": "set-complex",
  "nodeType": "set-variable",
  "parameters": {
    "variables": {
      "order": {
        "id": "{{ $json.id }}",
        "customer": {
          "name": "{{ $json.customerName }}",
          "email": "{{ $json.customerEmail }}"
        },
        "items": "{{ $json.items }}",
        "totals": {
          "subtotal": "{{ $json.subtotal }}",
          "tax": "{{ $json.tax }}",
          "total": "{{ $json.total }}"
        }
      }
    }
  }
}

Replace All Variables

{
  "id": "reset-variables",
  "nodeType": "set-variable",
  "parameters": {
    "variables": {
      "step": 1,
      "status": "processing"
    },
    "mode": "replace"
  }
}

Build from Previous Variable

{
  "id": "build-from-var",
  "nodeType": "set-variable",
  "parameters": {
    "variables": {
      "processedUserId": "{{ $context.variables.userId }}_processed",
      "incrementedCount": "{{ parseInt($context.variables.count) + 1 }}"
    }
  }
}

Accessing Variables in Subsequent Nodes

Once set, variables are available in other nodes:

{
  "id": "next-node",
  "nodeType": "http-request",
  "parameters": {
    "url": "{{ $context.variables.apiUrl }}",
    "method": "POST",
    "body": {
      "userId": "{{ $context.variables.userId }}",
      "email": "{{ $context.variables.userEmail }}"
    }
  }
}

Variable Scope

Variables are scoped to workflow execution:

• Available to all subsequent nodes in same execution
• Not persisted across executions
• Can be overwritten by later Set Variable nodes
• Lost when workflow completes

License

MIT