Load a JSON string into a data structure.
Also, create a new data structure and serialize it into JSON.

Use objects and arrays (as appropriate for your language)
and make sure your JSON is valid (https://jsonformatter.org).

(require 'cl-lib)
 
(cl-assert (fboundp 'json-parse-string))
(cl-assert (fboundp 'json-serialize))
 
(defvar example "{\"foo\": \"bar\", \"baz\": [1, 2, 3]}")
(defvar example-object '((foo . "bar") (baz . [1 2 3])))
 
;; decoding
(json-parse-string example) ;=> #s(hash-table [...]))
;; using json.el-style options
(json-parse-string example :object-type 'alist :null-object nil :false-object :json-false)
;;=> ((foo . "bar") (baz . [1 2 3]))
;; using plists for objects
(json-parse-string example :object-type 'plist) ;=> (:foo "bar" :baz [1 2 3])
 
;; encoding
(json-serialize example-object) ;=> "{\"foo\":\"bar\",\"baz\":[1,2,3]}"