Encodes a JSON map from a compile-time keyword.

Encodes the keys at compile time and strives to create as flat iodata structure as possible to achieve maximum efficiency. Does encoding right at the call site, but returns an %Jason.Fragment{} struct that needs to be passed to one of the "main" encoding functions - for example Jason.encode/2 for final encoding into JSON - this makes it completely transparent for most uses.

Only allows keys that do not require escaping in any of the supported encoding modes. This means only ASCII characters from the range 0x1F..0x7F excluding '\', '/' and '"' are allowed - this also excludes all control characters like newlines.

Preserves the order of the keys.

Example

iex> fragment = json_map(foo: 1, bar: 2)
iex> Jason.encode!(fragment)
"{\"foo\":1,\"bar\":2}"

Encodes a JSON map from a variable containing a map and a compile-time list of keys.

It is equivalent to calling Map.take/2 before encoding. Otherwise works similar to json_map/2.

Example

iex> map = %{a: 1, b: 2, c: 3}
iex> fragment = json_map_take(map, [:c, :b])
iex> Jason.encode!(fragment)
"{\"c\":3,\"b\":2}"