application.html.haml

// At the end of your layouts/application.html.haml file, convert the YAML Hash to a JS Hash:

:javascript
  window.I18n = #{sanitize(js_translations.to_json)}

en.yml

en:
  js:
    products:
      price: "Some text"

i18n.js

/*
  Use it by running t("products.price");
*/

window.t = function(key) {
  if(!key){
    return "N/A";
  }
  
  var keys = key.split(".");
  var comp = window.I18n;
  $(keys).each(function(_, value) {
    if(comp){
      comp = comp[value];
    }
  });

  if(!comp && console){
    console.debug("No translation found for key: " + key);
    return "N/A";
  }

  return comp;
};