Formula

Uncontrolled node

Overview

The Formula node evaluates mathematical expressions and performs calculations using the mathjs library. It dynamically generates input sockets based on the variables referenced in your formula expression, allowing you to create reusable calculation components that respond immediately to input changes.

When you type a formula like a + b or price * quantity, the node automatically creates corresponding input sockets (a, b, price, quantity) that can be connected to other nodes. The node evaluates the expression whenever any input value changes, making it ideal for real-time calculations, data transformations, and mathematical operations within your workflow.

Variable Scope

The Formula node has access to three levels of variables during evaluation:

• Node Inputs: Values connected to the dynamically generated input sockets
• Parent Workflow Variables: Variables set in the immediate parent workflow scope
• Root Workflow Variables: Global variables available throughout the entire workflow execution

If a variable exists in multiple scopes, the node follows the standard precedence: node inputs override parent variables, which override root workflow variables.

Inputs

Input	Type	Description	Default
Formula	Text	The mathematical expression to evaluate. Supports standard math operators (+, -, *, /, ^), functions (sin, cos, sqrt, etc.), and variables. Variables automatically become input sockets.	-
[Dynamic]	Data	Dynamically generated inputs based on variables detected in the formula field. For example, typing x * y creates x and y inputs.	-

Outputs

Output	Type	Description
Output	Data	The result of evaluating the formula expression. Returns undefined if the formula is empty or contains errors.

Runtime Behavior and Defaults

• Evaluation Engine: Uses mathjs for expression parsing and evaluation, supporting advanced mathematical functions, constants (pi, e), and complex expressions.
• Dynamic Input Generation: Input sockets are created or removed automatically when the formula text changes. Existing connections to removed inputs are deleted.
• Error Handling: If the formula contains syntax errors or references undefined variables, the node outputs undefined and logs the error to the console.
• Type Coercion: Input values are coerced to numbers where possible. Non-numeric inputs may result in NaN or undefined depending on the operation.
• Immediate Execution: As an uncontrolled node, it evaluates immediately whenever inputs change or the formula is modified, without requiring an event trigger.

Example

Basic Arithmetic

Formula: price * quantity

Inputs:

• price: 25.00
• quantity: 4

Output: 100

Using Workflow Variables

If you have workflow variables taxRate (0.08) and discount (5), you can reference them directly:

Formula: (subtotal * (1 + taxRate)) - discount

Inputs:

• subtotal: 100

Output: 103 (calculated as (100 * 1.08) - 5)

Complex Calculations

Formula: sqrt(pow(x, 2) + pow(y, 2))

Inputs:

• x: 3
• y: 4

Output: 5 (calculates the hypotenuse of a right triangle)

Variable Naming

Variable names in formulas must follow JavaScript identifier rules (start with letter/underscore, contain only letters, numbers, underscores). Avoid spaces or special characters in variable names.