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The .j namespace

JSON serialization

The .j namespace contains functions for converting between JSON and q dictionaries.

The .j namespace is reserved for use by KX, as are all single-letter namespaces.

Consider all undocumented functions in the namespace as its private API – and do not use them.

.j.j (serialize)

.j.j x

Where x is a K object, returns a string representing it in JSON.

.j.jd (serialize infinity)

.j.jd (x;d)


  • x is a K object
  • d is a dictionary

returns the result of .j.j unless d[null0w] is 1b, in which case0wand-0ware mapped to"null"`. (Since V3.6 2018.12.06.)

q).j.j -0w 0 1 2 3 0w
q).j.jd(-0w 0 1 2 3 0w;()!())
q).j.jd(-0w 0 1 2 3 0w;([null0w:1b]))

.j.k (deserialize)

.j.k x

Where x is a string containing JSON, returns a K object.

q).j.k 0N!.j.j `a`b!(0 1;("hello";"world"))        / dictionary
a| 0       1
b| "hello" "world"
q).j.k 0N!.j.j ([]a:1 2;b:`Greetings`Earthlings)   / table
a b
1 "Greetings"
2 "Earthlings"

Note serialization and deserialization to and from JSON may not preserve q datatype