Dump Output

The print() statement, as a node. Wire any value into JN_DumpOutput and it gets dumped out - to the console, effectively - with no Save Image, no Preview widget, no need to build a whole inspection pipeline just to see what's inside a wire. It's part of JNComfy (jn-jairo/jn_comfyui), and it's close kin to the pack's own README example: the "easy generic inputs" patch section literally demonstrates a tiny PrintValue node that prints whatever's connected to it. JN_DumpOutput is that idea, shipped as a real, usable node.

Why you'd reach for it

Debugging a ComfyUI graph usually means either reading a stack trace after something's already failed, or building an ad hoc chain of nodes to surface a value visually. Neither is great for the case where you just want to know "what's actually flowing through this wire right now" - a number, a string, an array from JN_PrimitiveStringToArray, the output of a JN_MathOperation. This node is the fast path: connect it, run the graph, read the value.

How it works

mode_repr is a required BOOLEAN (default false) that controls how the value gets formatted - off, you get the normal readable form; on, you get Python's repr()-style representation, which shows more structural detail (quotes around strings, exact type hints) at the cost of readability. title is an optional label, handy once you've got several Dump nodes in one graph and need to tell their output apart. value is what actually gets dumped, typed * so it accepts literally anything.

Unlike the rest of this pack's workflow-control family, this node has no flow/dependency inputs - it doesn't need manual sequencing, because it's already an output node (is_output_node=True), and it fires whenever its own value input is satisfied, following normal data-dependency scheduling.

The inputs and outputs that matter

• mode_repr (BOOLEAN, default false) - required. Toggle on for Python repr()-style output when you need to see exact types/quoting, leave off for a plainer dump.
• title (STRING, default empty, optional) - a label for this specific dump, useful with more than one in a graph.
• value (any type, optional) - the thing you actually want to see.

No outputs - this is a terminal node, the value goes to console/log, not forward into the graph.

How to install it

Via ComfyUI Manager: search "JNComfy", install, restart. Manually:

cd ComfyUI/custom_nodes
git clone https://github.com/jn-jairo/jn_comfyui

then restart ComfyUI. Small, single-author pack with no real community discussion we could find and no entry in our knowledge base - for a debug node this simple that's not much of a loss, but don't expect a support thread if you hit an edge case with the repr formatting.

Common issues & troubleshooting

Nothing shows up anywhere on the canvas. This node's output goes wherever this pack routes its console/log output, not to a widget on the node face necessarily - if you're expecting an in-canvas display like Preview Image gives you, check your server logs/terminal instead.

Output looks unreadable - brackets, quotes, escape characters everywhere. That's mode_repr turned on. Flip it off for a plain, human-readable dump; keep it on only when you specifically need to see exact string quoting or type structure.

You have several Dump nodes and can't tell which output is which. Set title on each one - it's exactly what that field is for.