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The loop node iterates over data, executing a set of nodes for each iteration. It supports three modes: iterating over arrays, running a fixed count, or looping while a condition is true.

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Configuration

{
  "id": "process_orders",
  "type": "loop",
  "config": {
    "items": "{{request.body.orders}}",
    "as": "order",
    "index": "i",
    "do": ["validate_order", "process_order"],
    "concurrent": false
  }
}

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Config Fields

FieldTypeRequiredDefaultDescription
itemsstring*-Template resolving to an array
countnumber/string*-Number of iterations or template
whilestring*-Condition to check each iteration
maxnumber**-Maximum iterations (required for while)
asstringNo"item"Variable name for current item
indexstringNo"index"Variable name for current index
dostring[]Yes-Node IDs to execute each iteration
concurrentbooleanNofalseRun iterations in parallel
* Must specify exactly one of: items, count, or while ** Required when using while mode

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Loop Modes

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Items Mode

Iterate over an array: 
{
  "id": "send_emails",
  "type": "loop",
  "config": {
    "items": "{{users}}",
    "as": "user",
    "index": "i",
    "do": ["send_email"]
  }
}
Inside the loop, access:
  • {{user}} - Current array element
  • {{i}} - Current index (0-based)

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Count Mode

Run a fixed number of times: 
{
  "id": "retry_request",
  "type": "loop",
  "config": {
    "count": 3,
    "index": "attempt",
    "do": ["make_request", "check_success"]
  }
}
Count can be a template: 
{
  "count": "{{request.body.quantity}}"
}

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While Mode

Loop while a condition is true: 
{
  "id": "paginate",
  "type": "loop",
  "config": {
    "while": "{{has_more_pages}} == true",
    "max": 100,
    "do": ["fetch_page", "check_more"]
  }
}
The max field is required to prevent infinite loops.

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Output

{
  "iterations": 5,
  "results": [
    { "index": 0, "output": { ... } },
    { "index": 1, "output": { ... } },
    { "index": 2, "output": { ... } },
    { "index": 3, "output": { ... } },
    { "index": 4, "output": { ... } }
  ],
  "completed": true,
  "error": null
}
FieldTypeDescription
iterationsnumberTotal iterations completed
resultsarrayOutput from each iteration
completedbooleanWhether loop finished normally
errorstringError message if loop failed

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Context Variables

During each iteration, these variables are available:
VariableDescription
{{item}} (or custom as)Current item (items mode) or iteration number (count mode)
{{index}} (or custom name)Zero-based iteration index

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Example Access

{
  "id": "process_item",
  "type": "http",
  "config": {
    "method": "POST",
    "url": "https://api.example.com/items",
    "body": {
      "item_id": "{{order.id}}",
      "iteration": "{{i}}"
    }
  }
}

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Examples

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Process Array Items

{
  "id": "process_all_orders",
  "type": "loop",
  "config": {
    "items": "{{fetch_orders.output.body}}",
    "as": "order",
    "do": ["validate_order", "save_order"]
  }
}

​
Concurrent Processing

Process items in parallel for better performance: 
{
  "id": "send_notifications",
  "type": "loop",
  "config": {
    "items": "{{subscribers}}",
    "as": "subscriber",
    "do": ["send_notification"],
    "concurrent": true
  }
}

​
Pagination Loop

Fetch all pages from a paginated API: 
[
  {
    "id": "init_pagination",
    "type": "set",
    "config": {
      "key": "page",
      "value": 1
    }
  },
  {
    "id": "init_has_more",
    "type": "set",
    "config": {
      "key": "has_more",
      "value": true
    }
  },
  {
    "id": "fetch_all_pages",
    "type": "loop",
    "config": {
      "while": "{{has_more}} == true",
      "max": 50,
      "do": ["fetch_page", "update_pagination"]
    }
  }
]

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Retry Pattern

Retry a request up to 3 times: 
{
  "id": "retry_api_call",
  "type": "loop",
  "config": {
    "count": 3,
    "index": "attempt",
    "do": ["make_request", "check_if_should_retry"]
  }
}

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Accessing Loop Results

After the loop, access results by index: 
{
  "id": "summarize",
  "type": "transform",
  "config": {
    "output": {
      "total_processed": "{{process_all_orders.output.iterations}}",
      "first_result": "{{process_all_orders.output.results[0]}}",
      "all_results": "{{process_all_orders.output.results}}"
    }
  }
}

​
Nested Data Access

When iterating over objects with nested data: 
{
  "id": "process_nested",
  "type": "loop",
  "config": {
    "items": "{{data.users}}",
    "as": "user",
    "do": ["process_user"]
  }
}
Inside process_user: 
{{user.name}}           -> Access user's name
{{user.address.city}}   -> Access nested properties
{{index}}               -> Current iteration index

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Performance Considerations

  1. Use concurrent: true for independent operations
  2. Set reasonable max for while loops to prevent runaway execution
  3. Batch operations when possible instead of individual API calls
  4. Limit iterations - very large loops can impact performance