function varType(mixed) { if (mixed === null) return "null"; var result = typeof mixed; return result; } module.exports = function (fields, object, value) { if (typeof fields !== "string") { throw new Error("Argument #1 expects a string, given " + varType(fields) + "."); } fields = fields.split("."); function levelUp(obj, field, value) { if (typeof obj[field] !== "undefined") { if (fields.length === 0) { // var oldVal = obj[field]; obj[field] = value; return value; } else { if (typeof obj[field] !== "object") { obj[field] = {}; } return levelUp(obj[field], fields.shift(), value); } } else { // keep going if necessary if (fields.length === 0) { obj[field] = value; return value; } else { // var newField = fields.shift() obj[field] = {}; // {newField: value} return levelUp(obj[field], fields.shift(), value); } } } return levelUp(object, fields.shift(), value); };