Enabling loop on a step

​
Enabling Loop

To enable looping for a step:
  1. Click the step’s options menu (⋮)
  2. Click Add Loop
  3. Enter a loop expression that determines how the step iterates

​
Loop Expression

  • A JavaScript expression that returns the next item to process
  • Returns null, undefined, or false to terminate the loop
  • Has access to special variables:
    • index: Current iteration number (starts at 0)
    • item: Current value being processed

​
Loop Output

  • When loop is enabled, the step’s output becomes an array
  • Each array element contains the output from one iteration
  • Output array maintains the order of processing

​
Loop Expression Rules

  • Return one item at a time from the array: return items[index];
  • Never return the full array (causes infinite loop)

​
Accessing Output

When a step has looping enabled, its output becomes an array containing results from each iteration: 
const results = modelStep.output.map((item) => item.message);
When accessing the output of a looped step in code steps, you must use array methods like map() to access individual iteration results.

​
Loop Termination

Loop stops when the expression returns null, undefined, or false. Array bounds automatically handle termination: 
return items[index]; // Returns undefined when index >= length

​
Examples

Here are some practical examples demonstrating how to use loops in your workflows:

​
Parallel API Requests

Process multiple API endpoints simultaneously: Parallel API Requests

​
File Batch Processing

Process multiple files with consistent logic: Files Batch Processing This eliminates the need for separate model steps for each file.

​
Object Properties Processing

For objects, you can loop through keys or values, so your loop expression should return an object with the key and value: 
const entries = Object.entries({
  apple: 'red',
  banana: 'yellow',
  orange: 'orange',
});

return entries[index]
  ? { key: entries[index][0], value: entries[index][1] }
  : null;
This approach lets you process each property with the same logic while maintaining property names.

​
Remove Loop

To remove a loop from a step:
  1. Click the step’s options menu (⋮)
  2. Click Remove Loop