How to access variable sent from Rails 4 controller in JavaScript?

Question

I have a @coords variable:

#maps controller
 def index
    @coords = Map.all
  end

Inside index.html.erb, I have:

<%= content_tag 'div', id: 'coords', data: @coords.to_json do %>

<% end %>

How my content_tag looks like after rendering HTML page:

[{"id":1,"vibration_level":456,"lat":"71.45543","lon":"53.43424","time_sent":"1994-05-20T00:00:00.000Z","created_at":"2015-06-13T06:53:30.789Z","updated_at":"2015-06-13T06:53:30.789Z"} ]

How can I access it from a JavaScript file.

Are you rendering it as text in a div? You need to render it in a script tag and assign it to a variable. Then any JavaScript code on the page can reference that variable. — David
– David, Commented Jun 13, 2015 at 11:57
@David, I tried that too, the problem is that my external script is loaded first, so it cant see my variable defined in html page. — yerassyl
– yerassyl, Commented Jun 13, 2015 at 12:03
Then load the scripts in the correct order. No language can reference a value before it's been defined, this isn't specific to Rails and/or JS. — David
– David, Commented Jun 13, 2015 at 12:04

caspg · Accepted Answer · 2015-06-13 12:34:35Z

1

You should consider using gon gem. This gem is for sending data from rails to your JavaScript.

You can do smth like this:

#map controller    
def index
  @coords = Map.all
  gon.coords = @coords.to_json
end

And then you can acces your variable in JS: gon.coords

answered Jun 13, 2015 at 12:34

caspg

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2 Comments

fuzzybabybunny Over a year ago

Personally, I think this is much better than sending an instance variable's contents as a string into a data- tag in the view and then hacking away with jQuery to grab the string and then parsing it back into an object. On a side note, would you happen to know if gon can send over any kind of data type? Like a function?

caspg Over a year ago

github.com/gazay/gon/wiki/Usage-example You can for sure pass int, array, hash, string.

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