json_template.coffee

###
# Below is a quick example of how CoffeeScript can be used to easily template JSON
#
# CoffeeScript has a few notable features for this role:
#
#   1. It has existential accessors, so you safely invoke nested properties w/o checking for their existence explicitly (`myObj.someOptionalProp?.someOtherOptProp?.val)
#   2. Using the "do" constrution you can execute anonymous functions that return objects in place, allowing fairly straightforward conditional json properties and other pre-processing.
#   3. Using multi-line object definitions and the underscore extend method, it's fairly literate to intermingle code with basic json values.
#   4. It's object notation is nice.
###

module.export = (locals) ->
  _({}).extend
    a: 3
    b: 2
    ,
    do () ->
      if locals.someProp
        somePropMappedKey: locals.someProp
    ,
    objProp:
      _({}).extend
        d: locals.d
        , do () ->
            if locals.someObj?.nestedProp
              nestedProp: locals.someObj?.nestedProp
    aryProp: do () ->
      prop.key for prop in locals.someArrayOfObjects

###
# This should result in an object like this:
#
#  {
#    a: 3,
#    b: 2,
#    somePropMappedKey: "value of locals.someProp",
#    objProp: {
#      d: "value of locals.d",
#      nestedProp: "value of someObj"
#   },
#   aryProp: [ "prop.key val 1", "prop.key val 2"]
# }
#
# This can then be run with code like this:
#
# template = require './templates/my-template'
# res.send template(locals)
#
# That code could be further exposed via a middleware-injected function res.renderJSON
###