I am developing a bootstrap application and I would like to do the following:
when a form is submitted, I want an incoming webhook from Slack to post the contents of the form to a slack channel.
Because I am using bootstrap, how would I go about creating this?
Would I use Javascript or Node.js?
There are different ways how to do that.
The standard approach is to use server based scripts. Your form calls a script on submit. In that script you read the form content on startup (e.g. input from GET request), build a Slack message out of it and send it to your incoming webhook on your Slack team. That is most commonly done with PHP, but other server based script languages like Python, node.js should work just as well.
Check out this article at W3School on how to read form data with PHP.
If you want to do it with Javascript you could attach your JS function to the submit event of your form, read the form content on submit, build a Slack message out of it and send it to your incoming webhook. I would use jQuery and AJAX for that, but it would also work with pure Javascript.
However, with Javascript you would have to expose the incoming webhook URL to the browser, which would potentially open your Slack team to SPAM. So I would suggest to stick with a server based solution.
Bootstrap is a set of CSS and Javascript that helps you make good looking and responsive websites, but does not have anything to do with sending form content to a webhook on Slack.