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Pass JavaScript variables to Rails controller

Google query doesn't give much useful result on this topic. What we discuss here is if there is a value/function getParameters() in JavaScript returns "message = hello_world" (a URL query). How do you pass the JS variable into controller?


Most common way is using link_to_remote which constructs an Ajax call, but the drawback is you have to handle the params[:message] using RJS template (or please let me know if I was wrong). Here is the example:

400: Invalid request

As you see, the :with option will eventually become :with => "message=hello_world". A new parameter is accessible by calling params[:message]. But what if I only want to render another page?

capture block

Capture block captures a variable for the view which can be reused. The idea is to call the JavaScript inside capture block to pass it as a Rails variable in view. The @param variable is readable in the view.

400: Invalid request


Remember that we have already passed the JavaScript value to @param variable, it is used here. An inline redirect_to does the trick, that redirects to the new action and value is accessible by calling params[:message].

400: Invalid request

I'm sure that you will have other ways of using these tricks in difference situation, but hope you get the idea and use them whenever is suitable.