gistfile1.js

This expects an input like:

<select data-id=<%= ri.id %>  ...other stuff...></select>


$(".some-input").change(function(){
  var ri_id = $(this).data('id')
  
  data = {
    amount : $(this).val()
  }
  
  $.post("/recipe_ingredients/"+ri_id, data, function(data){
    // this gets called if the function succeeds
  })
})