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An Easier Way to Enforce Required Parameters in ES6

Expands on Handling required parameters in ECMAScript 6 by Axel Rauschmayer.

The idea (which is credited to Allen Wirfs-Brock) is, in essence, to use default parameter values to call a function which throws an Error if the parameter is missing:

const throwIfMissing () => { throw new Error('Missing parameter') }

	'use strict';

	// simple express server
	var express = require('express');
	var app = express();
	var router = express.Router();

	app.use(express.static('public'));
	app.get('/', function(req, res) {
	res.sendfile('./public/index.html');

	<!doctype html>
	<html lang="en">
	<!--한글은 lang="ko" Learn more : https://www.w3.org/International/questions/qa-html-language-declarations-->
	<head>
	<meta charset="utf-8">
	<title></title>
	<meta name="description" content="">
	<meta name="author" content="">
	<meta name="keywords" content="">
	<meta name="viewport" content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0">