Using javascript data to populate rails params

Question

The following form is intended to submit data using HTML5 geolocation data.

The javascript

function geoOk(position)
{
  default_latitude = position.coords.latitude;
  default_longitude = position.coords.longitude;
  $('#my_latitude').html(default_latitude);
  $('#my_longitude').html(default_longitude);

properly generates data, which can be displayed in the view:

<span id="my_latitude"></span> => <span id="my_longitude"></span>

Now the form should generate params based on these JS generated variables. Hidden values are not possible as ERBs are generated server-side before the jasvascript generates any data.

<%= form_tag(:find_by_my_locations, method: :post) do %>
  <%= check_box_tag :location_ok, params[:location_ok] %><%= t('my_location_confirm') %><br />
  <%= submit_tag %>
<% end %>

How should can the params be generated for the next controller action?

jQuery is enabled on this application.

Edit

document.querySelector('#form_latitude').value = position.coords.latitude;
document.querySelector('#form_longitude').value = position.coords.longitude;

and form

  <%= hidden_field_tag "form_longitude" %> 
  <%= hidden_field_tag "form_latitude" %>

worked without requiring the document ready JS bloc

margo · Accepted Answer · 2015-12-31 10:17:03Z

1

Can you create another function once the document has loaded which can retrieve the required values via jquery and add them to a hidden field.

  $(document).ready(function(){
    var longitude = $("#longitude").text();
    $("#hidden_field").val(longitude);
  });

edited Dec 31, 2015 at 10:17

answered Dec 30, 2015 at 11:59

margo

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8 Comments

Jerome Over a year ago

the value is definitely not part of the params. The submit_tag may need an onClick handler?

margo Over a year ago

I'm not clear what's not working. As part of your rails view include a hidden field in the form which has an id e.g. <%= hidden_field_tag "form_longitude" %>. You can update the value of this field as part of the function geoOk. $('#form_longitude').val(default_longitude);

Jerome Over a year ago

Maybe I was not clear in my explanations. the form is being generated server-side. The javascript is being executed client-side and the the form cannot have its value defined as it does not yet exist. so somehow the variables needs to be passed only when a button is clicked, as then the value 'exists.

margo Over a year ago

How is the function geoOk triggered? If it happens after the document is loaded, as long as the value of the hidden field is updated after the geoOk function is called it should work. I did a test and the updated value gets passed in the params hash.

Jerome Over a year ago

Premise: when it come sot javascript, I am dense... getting to update the hidden_field via JS is truly opaque to me. do you have a JS fiddle where this test is apparent so I can try and understand it? THanx

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