(De-)Serializing JavaScript Models With Metaprogramming

README.md

compare before.js with after.js

after.js

import Record from "./record.js";

export default class Store extends Record {
	static get slots() {
		return {
			id: null,
			lists: collection(List)
		};
	}
}

class List extends Record {
	static get slots() {
		return {
			title: null,
			items: collection(Item)
		};
	}
}

class Item extends Record {
	static get slots() {
		return {
			caption: null,
			done: value => !!value
		};
	}
}

function collection(model) {
	return items => items.map(item => new model(item));
}

before.js

export default class Store {
	constructor(id, lists) {
		this.id = id;
		this.lists = lists;
	}

	toJSON() {
		let { id, lists } = this;
		return { id, lists };
	}

	static fromJSON({ id, lists }) {
		return new this(id, lists.map(list => List.fromJSON(list)));
	}
}

class List {
	constructor(title, items) {
		this.title = title;
		this.items = items;
	}

	toJSON() {
		let { title, items } = this;
		return { title, items };
	}

	static fromJSON({ title, items }) {
		return new this(title, items.map(item => Item.fromJSON(item)));
	}
}

class Item {
	constructor(caption, done = false) {
		this.caption = caption;
		this.done = done;
	}

	toJSON() {
		let { caption, done } = this;
		return { caption, done };
	}

	static fromJSON({ caption, done }) {
		return new this(caption, !!done);
	}
}

record.js

export default class Record {
	constructor(data) {
		let ctor = this.constructor;
		if(!ctor._initialized) { // generate accessors
			Object.entries(ctor.slots).forEach(([slot, handler]) => {
				makeGetter(ctor.prototype, slot, handler);
			});
			ctor._initialized = true;
		}

		this._data = data;
	}

	toJSON() {
		return this._data;
	}
}

function makeGetter(proto, slot, handler) {
	Object.defineProperty(proto, slot, {
		get() {
			let value = this._data[slot];
			return handler ? handler(value) : value;
		}
	});
}