ComfyUI-ForLoops

JkNodes — ForLoop

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Real in-graph loops for ComfyUI, in the JkNodes category.

These nodes use ComfyUI's graph-expansion execution model, so an entire loop runs inside a single Queue Prompt. Every loop is an Open / Close pair, and everything placed downstream of the Open node (up to Close) is repeated once per iteration — including sink nodes such as Save Image or Preview.

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Nodes

All four nodes live under the JkNodes category.

For Open / For Close

A counting loop, like Python range(start, end).

| Node | Inputs | Outputs | |------|--------|---------| | For Open | start, end, initial_value (optional) | flow, index, value | | For Close | flow, value (optional) | value |

• index emits start, start+1, … , end-1 (e.g. start=0, end=5 → 0,1,2,3,4).
• end is exclusive: the loop runs end − start times.

For Each Open / For Each Close

Iterate over up to 50 inputs of any type (like a typed "switch any"). Connect one input and the sockets/outputs adopt that type; a new empty slot is added automatically as you connect more.

| Node | Inputs | Outputs | |------|--------|---------| | For Each Open | value0 … value49 (dynamic), initial_value (optional) | flow, index, item, value | | For Each Close | flow, value (optional) | value |

• item is the current element for this iteration.
• index is the current 0-based position.

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How to wire a loop

For loop example

For Each loop example

For Open ──flow─────────────────────────────► For Close
        └─index/item─► [ your work … → Save Image ]

1. Drop a … Open node and its matching … Close node.
2. Connect Open flow → Close flow.
3. Drive your pipeline with Open index (For) or Open item (For Each).

That's it. Everything downstream of the Open node runs once per iteration, so a Save Image at the end of the pipeline fires once for every iteration.

Threading a value back (optional)

You can connect the result at the end of your pipeline into Close value. This is useful to:

• Force ordering — guarantees the whole pipeline finishes before the loop advances to the next iteration.
• Accumulate — Close value is fed back into Open initial_value on the next iteration, and the final value comes out of Close value when the loop ends.

A common, robust setup (recommended):

Open flow  ──────────────► Close flow
Open index ──► [ load line → generate → Save Image ] ──► Close value

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Example workflows

Drag a file from example_workflows/ onto the ComfyUI canvas:

• For_example.json — a range(0, 5) loop; Preview as Text shows the result.
• ForEach_example.json — iterates over three strings and concatenates them into one, showing how to accumulate across items.

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Notes & tips

• end is exclusive. If you have a file with N lines, set end = N to get indices 0 … N−1. If end ≤ start, the loop does not iterate.
• The flow wire is typed. A For flow cannot be plugged into a For Each Close (and vice-versa) — this is intentional, to prevent mismatched pairs.
• The internal _i socket is hidden by the bundled JavaScript; it carries the iteration counter and is managed automatically.
• This package uses the same execution mechanism as ComfyUI's official loop examples (graph expansion via comfy_execution.graph_utils.GraphBuilder).

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Installation

Place the ForLoops folder in ComfyUI/custom_nodes/ and restart ComfyUI. No extra dependencies are required.