Alternative to writing typedef for object definition and default parameters

[tmpmachine]

It assign null as default value and use less @type comment:

1. Create null factory that returns typedef (you'll need separate one for arrays):

/** @returns {Label|null} */ let Label = () => null  
/** @returns {Label[]|null} */ let Labels = () => null 

2. Use it with nullish operator:

// # example 1 - object
let book = Book() ?? {
  author: 'Super',
}

// # example 2 - array
let books = Books() ?? [];

// # example 4 - default parameter
function addPlayer(items = Players() ?? []) {
  // ...
}

Example:

// @ts-check

/**
@typedef {Object} Label
@property {string} [title] - An optional title for the label.

@typedef {Object} Book
@property {string} [name] - The name of the book.
@property {Label[]|null} [labels] - An array of labels associated with the book.
@property {string} [author] - The author of the book.

@typedef {Object} Player
@property {string} [name] - The name of the player.
@property {Player[]|null} [friends] - An array of the player's friends, or null if no friends.
/

/** @returns {Label|null} */ let Label = () => null  
/** @returns {Book|null} */ let Book = () => null  
/** @returns {Player|null} */ let Player = () => null  
/** @returns {Label[]|null} */ let Labels = () => null 
/** @returns {Book[]|null} */ let Books = () => null
/** @returns {Player[]|null} */ let Players = () => null


// # example 1 - object
let book = Book() ?? {
  author: 'Super',
}
console.log('book', book);


// # example 2 - array
let books = Books() ?? [];
books.push({
  author: 'Super',
  labels: [{
    title: 'Fantasy',
  }]
})
console.log('books', books);


// # example 3 - recursive
let player = Player() ?? {
  friends: [{
    friends: [{
      friends: [{
        name: 'Super'
      }]
    }]
  }]
}
console.log('player', player);


// # example 4 - default null parameter
function addPlayer(items = Players() ?? []) {
  items.push({
    name: 'Super',
  })
  return items;
}

let players = addPlayer();

console.log('players', players);