ES6 Features - based on examples from http://es6-features.org/

gistfile1.js

// Constants
const test_const = 1;

// Scoped variables - use `let` for local scope
let callbacks = [];
for (let i = 0; i < 3; ++i) {
  callbacks[i] = function() { return i; };
}

// Arrow functions
let plus_one = [1, 2, 3, 5].map(v => v + 1);

let fives = [];
[1, 4, 5, 6].forEach(v => {
  if (v % 5 === 0) {
    fives.push(v);
  }
});

// Arrow functions + Lexical "this" - A bit confusing actually...Ok, so arrow functions do not use their own "this"
this.fives = [];
this.nums = [1, 4, 5, 6];
this.nums.forEach((v) => {
  if (v % 5 === 0) {
    this.fives.push(v);
  }
});

// Function defaults
function f_with_defaults(x, y=7, z=42) {
  return x + y + z;
}
f_with_defaults(1) === 50;