Set an environment from html meta tags.

env.coffee

# Set an environment from html meta tags.
#
# Usage:
#
#     <meta name="ENV.station" content="swan" />
#     <meta name="ENV.port" content="2342" />
#
# The above meta tags would yield the following object:
#
#     ENV = {'station': 'swan', 'port': 2342}
#
# Notice how the type is coerced where applicable. If you have a meta tag that
# you don't want to coerce, you can opt out with:
#
#     <meta name="ENV.rawPort" content="2342" data-env-no-coerce />
#
# This would result in:
#
#     ENV = {'rawPort': '2342'}
#
# That's it!
ENV = {}
envRegex = /^ENV\./

elements = [].slice.call(document.getElementsByTagName('meta'))
elements = elements.filter (e) -> e.name.match(envRegex)

for element in elements
  propertyName = element.name.replace(envRegex, '')
  propertyValue = element.content

  try
    unless element.dataset.hasOwnProperty('envNoCoerce')
      eval("var __meta_env_eval__ = " + propertyValue)
      propertyValue = __meta_env_eval__
      delete __meta_env_eval__
  catch
    null
  finally
    ENV[propertyName] = propertyValue