How to filter keys of i18n-js only used in .js files

README.md

0. Prerequisites

You must use i18n-tasks and make sure i18n-tasks health is OK. I recommend that running i18n-tasks health along with your tests in CI.

1. Download i18n-tasks_js.rb as lib/i18n_tasks/js.rb in your project.

2. Insert the line below into the top of config/i18n-tasks.yml

<% require './lib/i18n_tasks/js' %>

3. You will see the js-keys command is installed.

$ i18n-tasks -h
...
    js-keys                          export i18n keys that used in js

4. Export js-keys.json

$ i18n-tasks js-keys > tmp/js-keys.json

5. Include js-keys.json as a only field like this.

translations:
- file: 'public/javascripts/path-to-your-messages-file.js'
  only: <%= File.read('tmp/js-keys.json') %>

Your i18n:js:export process may look like this:

i18n-tasks js-keys > tmp/js-keys.json && rake i18n:js:export

i18n-tasks_js.rb

# lib/i18n_tasks/js.rb
module I18nTasks
  module Js
    include ::I18n::Tasks::Command::Collection
    cmd :js_keys, desc: 'export i18n keys that used in js'
    def js_keys
      keys = []
      # keys used in js
      i18n.used_tree.nodes do |node|
        if node.leaf? && node.data[:occurrences].map(&:path).any? { |path| path =~ /\.js$/ }
          keys << node.key
        end
      end
      # keys that match `ignore_unused`
      i18n.data.get(:en).nodes do |node|
        if i18n.ignore_key?(node.key, :unused)
          keys << node.key
        end
      end
      # output result
      STDOUT.puts keys.map { |k| "*.#{k}" }.inspect
    end
  end
end
I18n::Tasks.add_commands I18nTasks::Js