Nested assignment of properties by dot delimited key string in CoffeeScript or JavaScript objects

nassign.coffee

# Naive recursive property assignment to object from a dot delimited string, e.g.
#
#   assignNestedPropertyByKeyString {}, 'biz', 'foo.bar.bah'
#       -> {foo: {bar: {bah: 'biz'}}}

assignNestedPropertyByKeyString = (obj, val, keyString) ->
    _assignNestedPropertyByKeyArray = (_o, _v, _keys) ->
        _k = _keys.splice 0, 1
        if _.isEmpty _keys
            _o[_k] = _v
        else
            _o[_k] = _o[_k] or {}
            _assignNestedPropertyByKeyArray _o[_k], _v, _keys

    if _.isEmpty keyString
        throw new Error "Have to have some key to assign"

    _assignNestedPropertyByKeyArray obj, val, keyString.split('.')


# Example application of the function with Lo-Dash

_.transform {'qux.gah.goh.box': 'ruh'}, assignNestedPropertyByKeyString
# -> {qux: {gah: {goh: {box: 'ruh'}}}}