Async and Practical

JSON Encode

Dart values to JSON text

jsonEncode from dart:convert walks a Dart Map/List/scalar and returns the equivalent JSON text. Maps preserve their insertion order and inner List values are encoded element by element.

Program

Play the program to build a small user map and encode it.

json_encode.dart
Replay: real traced execution (multi-file project)
import 'dart:convert';

void main() {
  var user = {'name': 'Ada', 'scores': [9, 12, 6]};
  var encoded = jsonEncode(user);
  print('json = $encoded');
}

  1. user ← {name: Ada, scores: [9, 12, 6]}

    3void main() {4  var user = {'name': 'Ada', 'scores': [9, 12, 6]};5  var encoded = jsonEncode(user);
    values this step{name: Ada, scores: [9, 12, 6]}user

  2. encoded ← {"name":"Ada","scores":[9,12,6]}

    4var user = {'name': 'Ada', 'scores': [9, 12, 6]};5var encoded = jsonEncode(user);6print('json = $encoded');
    values this step{"name":"Ada","scores":[9,12,6]}encoded

  3. print('json = $encoded');

    5  var encoded = jsonEncode(user);6  print('json = $encoded');7}
    outputjson = {"name":"Ada","scores":[9,12,6]}
    values this step{"name":"Ada","scores":[9,12,6]}encoded
dart:convert `import 'dart:convert'` brings in `jsonEncode` and `jsonDecode`.
jsonEncode `jsonEncode(value)` returns a JSON-text `String` representing the map, list, or scalar.
nested list The `scores` list is encoded element by element inside the surrounding object.