Simple event hook in TypeScript

events.ts

var template_escape = {"\\": "\\\\", "\n": "\\n", "\r": "\\r", "'": "\\'"}

var render_escape = {'&': '&amp;', '"': '&quot;', '<': '&lt;', '>': '&gt;'}

function escape_fn(data) {
	return (data || data === 0)
		? (data + '').replace(/[&\"<>]/g, (e) => render_escape[e])
    	: ''
}

function no_escape_fn(data) {
    return (data || data === 0)
		? (data + '')
		: ''
}

interface Template<T> {
	(data: T): string
}

function template<T>(tmpl): Template<T> {
	var render = new Function("_", "e", "$e", "return '" +
		tmpl
			.replace(/[\\\n\r']/g, (escape) => template_escape[escape])
			.replace(/{(\$?)\s*([\w\.]+)\s*}/g,
			"'+(function(){try{return $1e(_.$2)}catch(e){return ''}})()+'") + "'"
		)

	return function (data) {
		return render(data, escape_fn, no_escape_fn)
	}
}

var tpl = template<{ foo: string; bar: string }>('<foo>{foo}</foo><bar>{$bar}</bar>');
console.log(tpl({foo: "Hello & World", bar: "Hello &nbsp; World"}))

// 

interface Hook<Event> {
	(handler: { (event: Event): void }): void
	(event: Event): void
}

function hook<Event>(): Hook<Event> {
    var _handlers: Array<Function> = []
	var _busy = false

    function invoke() {
		if (arguments[0] instanceof Function) {
			_handlers.push(arguments[0]);
		} else if (!_busy) {
			_busy = true
			for (var i = 0; i < _handlers.length; i++) {
				_handlers[i].apply(this, arguments)
			}
			_busy = false
		}
    }

    return <Hook<Event>> invoke;
}

// EXAMPLE:
 
interface LoginEvent {
	username: string
	success: boolean
}

var onLogin = hook<LoginEvent>()

onLogin(event => console.log("Logged in: " + event.username))

onLogin({ username: 'Rasmus', success: true })