custom_option_data_type and custom_option_html_type JavaScript methods in Common.js use English field names

These two variables:

var html_type_name = html_type.options[html_type.selectedIndex].text;
var data_type_name = data_type.options[data_type.selectedIndex].text;

extract English labels and compare extracted value to explicit string, for example:

if (data_type_name == "Alphanumeric")

When running any translated version of CiviCRM, this condition does not work. The solution would be to assign some kind of id to HTML elements and use them to compare instead.