Article Type: Troubleshooting
Audience: Developers, Solution Architects, Power Users
Module: Data Flows → Script Editor
Applies to Versions: 2024.1+

1. Problem Overview

Developers frequently encounter errors when attempting to use standard JavaScript code in the Fuuz Script Editor. Code that works perfectly in Node.js, browser consoles, or other JavaScript environments fails with "not defined" errors when executed in Fuuz Data Flows.

This commonly occurs when developers copy code from external sources, use AI-generated JavaScript, or attempt to reuse existing transformation logic from other platforms.

Symptoms

• ReferenceError: payload is not defined
• ReferenceError: context is not defined
• ReferenceError: input is not defined
• ReferenceError: data is not defined
• Script executes but returns undefined
• Function definitions execute without producing output

2. Root Cause Analysis

The Fuuz Script Editor provides a controlled JavaScript execution environment that differs from standard JavaScript runtimes in several key ways:

3. Common Issues & Quick Fixes

4. Detailed Example: Converting Standard JavaScript

The following real-world example demonstrates a comprehensive OEE (Overall Equipment Effectiveness) calculation script that was originally written using standard JavaScript patterns. We'll walk through the specific changes required to make it work in the Fuuz Script Editor.

4.1 Original Code (Does NOT Work)

This code was generated using standard JavaScript conventions. It wraps logic in a function and expects payload and context as parameters:

// ❌ THIS CODE WILL FAIL IN FUUZ
function calculateOEE(payload, context) {
  // Helper function passes context as parameter
  function calculateOEEMetrics(stats, context, isWorkOrder = false) {
    if (isWorkOrder) {
      const woConfig = context.work_orders[workOrder];  // ❌ context.
      const product = context.products[woConfig.product];  // ❌ context.
      // ...
    }
  }
  
  // Process production records using payload parameter
  payload.production_records.forEach(record => {  // ❌ payload.
    // ...
    if (!workOrderStats[workOrder]) {
      const woConfig = context.work_orders[workOrder];  // ❌ context.
      const product = context.products[woConfig.product];  // ❌ context.
      // ...
    }
  });
  
  // Process workUnit history
  payload.workUnit_history.forEach(record => {  // ❌ payload.
    // ...
  });
  
  // Calculate metrics passing context to helper
  const shiftOEE = Object.values(shiftStats).map(s => 
    calculateOEEMetrics(s, context)  // ❌ passing context
  );
  
  return { /* results */ };
}

4.2 Problems Identified

4.3 Corrected Code (Works in Fuuz)

After applying the required transformations, the script executes successfully:

// ✅ THIS CODE WORKS IN FUUZ

// Helper functions remain as internal functions (no context parameter)
function getShift(dateTime) {
  const date = new Date(dateTime);
  const hour = date.getUTCHours();
  if (hour >= 6 && hour < 14) return 'Shift-1';
  if (hour >= 14 && hour < 22) return 'Shift-2';
  return 'Shift-3';
}

// Helper function accesses context globals directly
function calculateOEEMetrics(stats, isWorkOrder = false) {  // ✅ No context parameter
  if (isWorkOrder) {
    const woConfig = $work_orders[stats.workOrder];  // ✅ $work_orders
    const product = $products[woConfig.product];  // ✅ $products
    // ...
  }
}

// Initialize structures
const workUnitStats = {};
const shiftStats = {};

// Process production records using $ for payload
$.production_records.forEach(record => {  // ✅ $.
  // ...
  if (!workOrderStats[workOrder]) {
    const woConfig = $work_orders[workOrder];  // ✅ $work_orders
    const product = $products[woConfig.product];  // ✅ $products
    // ...
  }
});

// Process workUnit history
$.workUnit_history.forEach(record => {  // ✅ $.
  // ...
});

// Calculate metrics - no context parameter needed
const shiftOEE = Object.values(shiftStats).map(s => 
  calculateOEEMetrics(s)  // ✅ No context passed
);

// Explicit return statement
return {  // ✅ Required return
  summary: { /* ... */ },
  oee: { byShift: shiftOEE, /* ... */ },
  // ...
};

5. Step-by-Step Conversion Checklist

Follow this checklist when converting standard JavaScript to Fuuz-compatible code:

Step 1: Remove Function Wrappers

If your code is wrapped in a main function like function processData(payload, context), remove the function declaration and closing brace. The code should execute directly.

// Before:
function processData(payload, context) {
  // ... logic ...
  return result;
}

// After:
// ... logic ...
return result;

Step 2: Replace Payload References

Use find-and-replace to convert all payload access patterns:

Step 3: Replace Context References

Context data requires more careful replacement since each key becomes a separate global:

Step 4: Update Helper Function Signatures

Remove context from any helper function parameters and their call sites:

// Before:
function calculateMetrics(stats, context, isWorkOrder) {
  const config = context.work_orders[stats.workOrder];
  // ...
}
const result = calculateMetrics(data, context, true);

// After:
function calculateMetrics(stats, isWorkOrder) {
  const config = $work_orders[stats.workOrder];  // Access global directly
  // ...
}
const result = calculateMetrics(data, true);

Step 5: Ensure Return Statement Exists

Verify your script ends with an explicit return statement:

// Your processing logic...

// Must have explicit return at the end
return {
  summary: productionSummary,
  oee: { byShift: shiftOEE, byDay: dayOEE },
  insights: { avgOEE: calculatedAverage }
};

6. Key Considerations for Fuuz Development

When developing JavaScript scripts for the Fuuz platform, keep these important points in mind:

6.1 Execution Model

• Direct Execution: Code runs immediately – no function calls required
• Sandboxed Environment: Standard browser/Node.js APIs may not be available
• Synchronous Processing: Scripts execute synchronously; async/await patterns require special handling

6.2 Data Access Patterns

6.3 Built-in Helper Functions

Fuuz provides numerous built-in helpers accessible via $functionName(). Before importing external libraries or writing custom utilities, check if a built-in function exists:

• $moment() for date/time operations (Moment.js)
• $groupBy(), $uniq(), $flatten() for array operations
• $uuid(), $cuid() for ID generation
• $camelCase(), $snakeCase() for string transformations

6.4 Testing Strategy

• Use the Diagnostic Script: Start with a simple script to verify your environment
• Incremental Development: Build and test in small increments
• Console Output: Use the Console panel to inspect intermediate values
• Environment Isolation: Test thoroughly in Build before deploying to QA or Production

6.5 Working with AI-Generated Code

When using AI tools to generate JavaScript for Fuuz:

• Specify that payload data is accessed via $ (not payload)
• Specify that context data is accessed via $keyName globals
• Request direct execution (no function wrapper)
• Always validate the output follows Fuuz patterns before execution

7. Related Resources

• Fuuz Script Editor – JavaScript Development Guide
• Data Flow Designer Documentation
• JSONata Expression Reference
• Moment.js Documentation (for $moment functions)

8. Revision History

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