immutable groceries

index.js

// js

const groceries = {
  fruit: ['apple', 'orange', 'grapes'],
};

const newGroceries = {
  ...groceries,
  fruit: [
    ...groceries.fruit,
    'lychee'
  ]
}

console.log(groceries)
console.log(newGroceries)

main.dart

//dart

void main() {
  Map groceries = {
    'fruit': ['apple', 'orange', 'grapes'],
  };

  Map newGroceries = Map()
    ..addAll(groceries)
    ..update(
        'fruit',
        (_) => []
          ..addAll(groceries['fruit'])
          ..add('lychee'));

  print(groceries);
  print(newGroceries);
  
}