package.json

{
  "dependencies": {
    "lodash": "^3.10.1",
    "yamljs": "^0.2.3"
  }
}

x.js

YAML = require('yamljs');
_ = require('lodash');

en = YAML.load('/home/simon/src/openstreetmap-website/config/locales/en.yml').en;

// obtained using $ ag --nofilename  'flash\[.*='
danger = [
  "message.delete.deleted"
  ,"message.new.limit_exceeded"
  ,"message.new.message_sent"
  ,"message.read.wrong_user"
  ,"message.reply.wrong_user"
  ,"oauth_clients.create.flash"
  ,"oauth_clients.destroy.flash"
  ,"oauth_clients.update.flash"
  ,"trace.create.trace_uploaded"
  ,"trace.delete.scheduled_for_deletion"
  ,"trace.trace_header.traces_waiting"
  ,"trace.view.trace_not_found"
  ,"trace.view.trace_not_found"
  ,"user.confirm_email.failure"
  ,"user.confirm_email.success"
  ,"user.confirm_email.unknown_token"
  ,"user.confirm_resend.failure"
  ,"user.confirm_resend.success"
  ,"user.go_public.flash success"
  ,"user.lost_password.notice email on way"
  ,"user.make_friend.already_a_friend"
  ,"user.make_friend.success"
  ,"user.new.terms accepted"
  ,"user.new.terms declined"
  ,"user.new.terms declined url"
  ,"user.remove_friend.not_a_friend"
  ,"user.remove_friend.success"
  ,"user.reset_password.flash changed"
  ,"user.reset_password.flash token bad"
  ,"user.terms.you need to accept or decline"
  ,"user_block.revoke.flash"
  ,"user_role.filter.not_an_administrator"
  ,"application.require_moderator.not_a_moderator"
  ,"oauth.revoke.flash"
  ,"redaction.create.flash"
  ,"redaction.destroy.error"
  ,"redaction.destroy.flash"
  ,"redaction.destroy.not_empty"
  ,"redaction.update.flash"
  ,"user.auth_failure"
  ,"user.confirm.already active"
  ,"user.confirm.success"
  ,"user.confirm.unknown token"
  ,"user.filter.not_an_administrator"
  ,"user.filter.not_an_administrator"
  ,"user_block.create.flash"
  ,"user_block.filter.block_expired"
  ,"user_block.filter.block_period"
  ,"user_block.update.only_creator_can_edit"
  ,"user_block.update.success"
  ,"user_role.filter.already_has_role"
  ,"user_role.filter.doesnt_have_role"
  ,"user_role.filter.not_a_role"
  ];

  danger.map(function(d) {
    var str = _.pluck([en], d.split(/\./));
    if (/</.test(str)) console.log(d);
  });