How to create custom code to create a node
i wantd to trigeer post api how to creat a custome code in n8n selfhosted
Hi @Sale.Favourite_fab 
Welcome to the community!
You can find guidelines on how to create your own node in this tutorial: Build a node | n8n Docs
That should get you started! If you run into any troubles, feel free to post on the forums with details of where you’re stuck. Happy building!
i’m looking for custom function any code you can provide as examples
I don’t have any direct examples, but this tutorial in particular is probably the most helpful to you: Tutorial: Build a programmatic-style node | n8n Docs
Quick edit: This video might also help you 
Learn how to build your own n8n nodes - YouTube