I'm writing a node.js bot for IRC and I want it to post links in IRC that people can click on to prompt it to post more data (this is because I want to allow IRC users to stay on the channel, yet prevent my bot from having to flood the channel and get banned for spamming). Is there a way from a node.js application / server that will prevent the <a> tag in IRC from opening a new page? Or possibly a method within IRC for editing the appearance of a link, so I can actually tell the link to execute a javascript command instead?
This is not possible due to the huge number of different IRC clients and what extensions they support. IRC is a plain text-only service and a standard compliant IRC client can simply display what messages are sent to it directly without needing to apply any formatting. The common mIRC formatting extension does not have support for links either.
This means that most IRC clients will have no support for links (Except maybe autogenerated ones) nor javascript. Simply having support for an <a> tag for whatever reason is nonstandard behaviour and I do not know of any IRC clients that support it
An alternative would be to put a message in the bot output to ask the user to PM the bot with a specific message for more information.
EDIT: Replies to each individual question
Is there a way from a node.js application / server that will prevent the <a> tag in IRC from opening a new page?
This highly depends on what your client support for the <a> tag is. If your client supports the common HTML attributes for the <a> tag, then setting target="_self" will do it. You will need to provide more details about the client you are using to access the server with for a proper answer to this question.
Or possibly a method within IRC for editing the appearance of a link, so I can actually tell the link to execute a javascript command instead?
This is also highly dependant on the client. If we continue to assume that the client has support for all the standard HTML attributes, then <a href="#" onclick="[javascript goes here]; return false" style="[styling for link goes here]">Link Text</a> will work. Again, you will need to provide more details about the client for a better answer