Observations

var odds = evens.map(v => v + 1)

GET`http://foo.org/bar?a=${a}&b=${b}
    Content-Type: application/json
    X-Credentials: ${credentials}
    { "foo": ${foo},
      "bar": ${bar}}`(myOnReadyStateChangeHandler)

var [a, , b] = [1,2,3]

function f(x, y=12) { return x + y }
f(3) == 15

function f(x, ...y) { return x * y.length }
f(3, "hello", true) == 6

const x = "dont change me"

var arr = []
for (var i = 10; l--;) {
  let j = i
  result[i] = function() { return j }
}

arr[5]() === 5
arr[6]() === 6

var cat = 'Pavlova'
var dog = 'Charlie'
var pets = {cat, dog}

var s = new Set()
s.add("hello").add("goodbye").add("hello")
s.size === 2
s.has("hello") === true

var squares = [ x*x for (x of [1,2,3,4,5]) if (x % 2 == 1) ]

"abc".repeat(3).contains("cabca")

// tail call
function factorial(n, acc = 1) {
    'use strict';
    if (n <= 1) return acc;
    return factorial(n - 1, n * acc);
}
factorial(100000)

this one says "too much recursion

	function changeLanguageOrder(){
		if(null!=document.documentElement.lang && null!=document.getElementById('selectedLanguage')){
			if(document.documentElement.lang=="es"){
				document.getElementById('selectedLanguage').options[1].selected=true;
			}
			else if(document.documentElement.lang=="ht"){
				document.getElementById('selectedLanguage').options[2].selected=true;
			}
			else if(document.documentElement.lang=="il"){
				document.getElementById('selectedLanguage').options[3].selected=true;
			}
			else if(document.documentElement.lang=="ko"){
				document.getElementById('selectedLanguage').options[4].selected=true;
			}
			else if(document.documentElement.lang=="tl"){
				document.getElementById('selectedLanguage').options[5].selected=true;
			}
			else if(document.documentElement.lang=="vi"){
				document.getElementById('selectedLanguage').options[6].selected=true;
			}
			else if(document.documentElement.lang=="zh" || document.documentElement.lang=="zt"){
				document.getElementById('selectedLanguage').options[7].selected=true;
			}
			else { 
				document.getElementById('selectedLanguage').options[0].selected=true;
			}
		}

function New(name) { return java.lang.Class.forName(name).newInstance() }

function newList() { return New("java.util.LinkedList") }