How to assign and access a javascript variable in Rails using ajax

Question

I'm using the gon gem for rails, which allows you to save variables defined in a controller action and use them in your JavaScript. It works fine when I use it in non-Ajax settings, however, I'm having an issue with using it successfully when doing Ajax requests.

The problem: Ruby variables I assign to gon variables in the controller action when making Ajax requests come out as 'undefined' in the JavaScript.

The objective: I want to trigger an Ajax request on my page, which: 1) hits an action in the controller, and assigns a Ruby variable to a gon variable. 2) it then renders a js.erb file which executes JavaScript, part of which needs to take the Ruby variable defined in step 1, and treat it as a js variable.

here's the example action in step 1:

def some_action
 gon.my_ajax_var = {some: 'info'}
end

here's the example js.erb file it renders:

/some_action.js.erb

console.log('gon.my_ajax_var equals ' + gon.my_ajax_var)  //this doesn't work! comes out as 'undefined' when I expected {some: 'info'}

Any thoughts on how I fix this? I took a look at the gon.watch page, but I was confused as to whether that relates to this problem I'm having and how to implement the correct solution. Additionally, if there's a better way to do this without gon, I'm open to that as well.

Thanks!

Yanik Jay · Accepted Answer · 2014-01-20 22:45:56Z

2

I ended up solving this by doing the following:

In my controller:

def some_action
  @my_ajax_var = {some: 'info'}.to_json
end

In my corresponding view: /some_action.js.erb

var my_ajax_var = <%= @my_ajax_var.html_safe %>

Would've been nice to have piggybacked off the gon gem, but this got the job done.

answered Jan 20, 2014 at 22:45

Yanik Jay

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Comments

friedi · Accepted Answer · 2014-01-20 18:36:10Z

-1

It's some time ago that I used erb templates, but I think you need to add tags in your erb-file.

/some_action.js.erb

console.log('gon.my_ajax_var equals ' + <%= gon.my_ajax_var %>)

answered Jan 20, 2014 at 18:36

friedi

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1 Comment

Yanik Jay Over a year ago

friedi, just tried that, but this error was thrown: "undefined local variable or method `gon' for #<<Class:0x007fbfea377240>:0x007fbfe91c9958>". That error makes sense to me, as gon is supposed to only be defined as a js variable and not a ruby variable.

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