how can I use AJAX to pass JS variables to the controller?

Question

I'm using Ruby 2.0 and Rails 4.

I need to pass the value of certain JS variable obtained by a JS function to a controller to add it as a record in DB, I'm currently using several datatables to display information, the user selects a row in a datatable and pressing the next button then get the id of the selected rows and add it to a table in the DB as a row and another datatable shown, the thing is I do not want neither to use forms nor that the page is refreshed, and that all information that is presented is loaded at startup in view, I do a "presave" of selection in each step (datatable) without the user knowing.

now I can get the values of the selected rows in the view and present then in a Hidden_field, i need to get the value that hidden_field in the controller

i have read than AJAX can do the work, but i've not worked with ajax before.

some code:

script.js (in coffee)

leaveAStepCallback =(obj, context) ->
  alert("Leaving step " + context.fromStep + " to go to step " + context.toStep);
  ret=false
  if (context.fromStep==1 and context.toStep==2)
    document.getElementById('selec1').value= fnGetIdsOfSelectedRows fnGetSelected(oTable1), oTable1 #//get selected rows
    ret=true

in some_controller.rb need some like:

def pre_save
  if params[:step]=='1' #hidden_Field with step number
    @selrow=params[:selec1].to_s.split(',') #selected rows as '1,2,5,7'
    i=0
    while i<@selrow.length
      [email protected](i).to_i #selected row number

      addp=PreSaveTable.new #table to record each selected row
      addp.id_row=pr
      addp.save #save as row in table 
      i=i+1
    end

  end

end

some help?

Richard Peck · Accepted Answer · 2014-03-17 11:06:49Z

I've not worked with ajax before

Let me explain:

Asynchronous Javascript & XML

Ajax requests are sent with technology like Javascript to send requests to your server out of the typical HTTP request scope. This means you're able to create pseudo "live" functionality -- no refresh

Using ajax is especially simple with JQuery:

$.ajax({
    url: "your_endpoint",
    data: "your_serialized_data",
    success: function(data) {
        //code on success
    },
    error: function(data) {
        //code on error
    }
});

Code

#javascript
$(document).on("event", "element", function(e){
    $.ajax({
       url: "controller/action", 
       data: $("hidden_field").val().serialize()
    });
});

#controller
def pre_save
  if params[:step] == '1' #hidden_Field with step number
    @selrow = params[:selec1].to_s.split(',') #selected rows as '1,2,5,7'
    i=0
    while i < @selrow.length
      [email protected](i).to_i #selected row number

      addp=PreSaveTable.new #table to record each selected row
      addp.id_row=pr
      addp.save #save as row in table 
      i=i+1
    end

    respond_to do |format| 
       format.html 
       format.js #-> loads views/controller/pre_save.js.erb
    end

end

#app/views/controller/pre_save.js.erb
alert("Presave Complete!");

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