Rails: "null" instead of an array with 3 elements when trying to use ruby array in javascript

Question

I have this code-snippet:

in my app/assets/javascripts/application.js

//= require jquery
//= require harddisk
//= require rails-ujs
//= require_tree .

in my app/assets/javascripts/harddisk.js.erb

  var harddisk_locations = [<%= raw @harddisk_locations.to_json %>];
  console.log(harddisk_locations);

in my app/models/harddisk.rb

@harddisk_locations = ["foo", "bar", "baz"];

But for some reason on the harddisk page in browser console

@harddisk_locations is null instead of an array with 3 elements.

Why is it so and how to fix?

It doesn't help if I move the

@harddisk_locations = ["foo", "bar", "baz"];

from harddisk-model into harddisks_controller.rb

Try moving the file harddisk.js.erb in views: stackoverflow.com/questions/18437282/… and also @harddisk_locations in controller. — iGian
– iGian, Commented Sep 3, 2018 at 13:49

Ravi Teja Dandu · Accepted Answer · 2018-09-03 13:55:29Z

1

You should be defining them to a global variable instead of an instance variable. You can change your model code to:

HD_LOCATIONS = ['foo', 'bar', 'baz']

and in you JS file:

var harddisk_locations = [<%= raw Harddisk::HD_LOCATIONS.to_json %>];

answered Sep 3, 2018 at 13:50

Ravi Teja Dandu

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2 Comments

then I get an error: "uninitialized constant ERB::HD_LOCATIONS"

I have updated my code. Could you please try it once and in case it throws an error, paste the exception stack?