Liquid token can't access Object dynamicaly

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require 'json'

module Jekyll
  class ImageTag < Liquid::Tag

    def initialize(tag_name, name, tokens)
      super
      @name = name

      @file = File.read('manifest.json')
      @data_hash = JSON.parse(@file) 
      puts @data_hash // => { "0.js"=>"js/0.js" }
    end

    def render(context)
      a = "0.js"
      puts a // => 0.js
      puts @name // => 0.js
      puts a.class // => String
      puts @name.class // => Liquid::Token
      puts @data_hash[@name] // => Empty string ??!? But it should be js/0.js
      puts @data_hash[a] // => js/0.js
    end
  end
end

Liquid::Template.register_tag('image', Jekyll::ImageTag)

In my .html file:

<img src="{% image 0.js %}" alt="">

Should I convert the name argument into String? How should I do this?

Thank you