Using previous item output in loop

[Joachim_Brindeau]

Hello,

I am using a loop to generate content using the LLM node and I want my writing style to be consistent even though I am using loop to generate each section.

Right now, I am cheating by processing item 1 first, and looping all following items using this first processed item as guideline for the style of the content:

For various reasons (writing transitions from previous section, keeping numbering of headings consistent, etc.), I would like to loop using the output of the previous item if it exists.

So I was wondering if there is a way to use the N-1 item output when generating output for item N in the loop.

Thank you very much for your advice!
Cheers,
Joachim

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[ihortom]

@Joachim_Brindeau , yes, you can achieve it by utilizing $runIndex, something like this assuming one item is iterated each time

{{ $('Loop Over Items').first(1, $runIndex - 1) }}

See Output of other nodes for details.

In short,

• first(): applies to the first and hopefully single item in the loop
• 1 refers to the output “loop” of the loop node
• $runIndex refers to the current iteration (zero-based)

Therefore, you also need to add a check to prevent referencing the loop on the 1st iteration.

[Joachim_Brindeau]

Hi @ihortom

Thanks a lot for this, it’s almost what I want.

For clarity, I try to retrieve the output of the N-1 item as processed by the loop, not as it enters the loop. Thus, if I use the output of the loop node, it does not quite work as I intended.

Please find here a minimal workflow to show where I am stuck:

The expression I am trying to use is as follows:
{{ $runIndex = 1 ? $('test').first(0, $runIndex - 1).json.text : '' }}

How can I reference to the output of a node inside the loop without triggering the error below?

Referenced node is unexecuted
An expression references the node ‘section_generate’, but it hasn’t been executed yet. Either change the expression, or re-wire your workflow to make sure that node executes first.

I understand from @barn4k’s answer, on another post, that it’s unavoidable behavior at this stage

Conditional executed nodes break if node

Currently there is no other way. If you will try to refer to any node, that hasn’t been executed, you will receive that error.

But I cannot figure out an alternative workflow for my needs.

Thank you very much for your help
Cheers

[Joachim_Brindeau]

Solved!

I asked Claude to help me write a script to concatenate the output of the loop node and the output of the last item’s test node in the same JSON.

Took a few trials (a lot if I’m being honest) but it works and I can properly reuse the output of any node within the loop from previous items.

Here is the workflow:

Here is the script:

const newItems = [];

for (let i = 0; i < items.length; i++) {
  const item = items[i];
  
  // Get the JSON from the "test" node of the previous item, if it exists
  let previousItemTestJson = null;
  if ($runIndex > 0) {
    previousItemTestJson = $('test').first(0, $runIndex - 1).json;
  }
  
  // Get the JSON from the last node of the current item in the loop
  const loopJson = item.json;
  
  // Create a new object with both JSON data
  const newItem = {
    previousItemTestJson: previousItemTestJson,
    loopJson: loopJson
  };
  
  newItems.push(newItem);
}

return newItems;

and here it’s working: