ejson

Extended JSON library; used in Meteor's Distributed Data Protocol.

EJSON is a way of embedding more than the built-in JSON types in JSON. It supports all types built into JSON as plain JSON, plus the following:

Dates:

{"$date": MILLISECONDS_SINCE_EPOCH}

Binary data:

{"$binary": BASE_64_STRING}

(The base 64 string has + and / as characters 62 and 63, and has no maximum line length)

Escaped things that might otherwise look like EJSON types:

{"$escape": THING}

For example, here is the JSON value {$date: 10000} stored in EJSON:

{"$escape": {"$date": 10000}}

Note that escaping only causes keys to be literal for one level down; you can have further EJSON inside. For example, the following is the key $date mapped to a Date object:

{"$escape": {"$date": {"$date": 32491}}}

User-specified types:

{"$type": TYPENAME, "$value": VALUE}

Meteor ObjectIDs

Support for the "oid" custom type used for Meteor ObjectIDs is built-in:

{"$type": "oid", "$value": "c896e40bf6e51bbdc9adcf59"}

ObjectIDs may also be constructed:

// Create a new Random ID
ObjID = new EJSON.ObjectID()

// Create an ID with a known value
myID = new EJSON.ObjectID("c896e40bf6e51bbdc9adcf59")

Implementations of EJSON should try to preserve key order where they can. Users of EJSON should not rely on key order, if possible.

MongoDB relies on key order. When using EJSON with MongoDB, the implementation of EJSON must preserve key order.