TypeScript property decorator example

property_decorators_part_2.2.ts

"use strict";

/**
 * Декоратор для логирования свойств
 * @param target
 * @param key
 */
function logprop(target:any, key:string):any {

	var val:any,
		pool:{} = {},
		kn:string,
		isStatic:boolean = target.hasOwnProperty(key);

	if (isStatic) {
		val = target[key]
	}
	else {
		kn = target.constructor.name;
		if (!pool[kn]     ) pool[kn] = {};
		if (!pool[kn][key]) pool[kn][key] = null;
		val = pool[kn][key];
	}

	const get = ():any => {
		console.log(`Get: ${key} => ${val}`);
		return val;
	};

	const set = (newVal):void => {
		console.log(`Set: ${key} => ${newVal}`);
		val = newVal;
	};

	if (target.hasOwnProperty(key))
		return { get, set };

	if (delete pool[kn][key])
		Object.defineProperty(target, key, { get, set });
}

class Person {

	@logprop public name:string;
	@logprop public surname:string;

	@logprop public static vip:boolean = false;

	constructor(name:string, surname:string) {
		this.name = name;
		this.surname = surname;
	}
}


let me = new Person("Alex", "Mayorov");
me.name = "Alexander M.";
me.name;
Person.vip;
Person.vip = true;
Person.vip;