http://espadrine.github.io/New-In-A-Spec/es6/
EcmaScript Sixth Edition
let, const (define block-local vars), function in block scope
destructuring: let {x, y} = pt; let [s, v, o] = triple(); (assuming let pt = {x:2, y:-5}, for instance).
parameter default values: function f(x, y=1, z=0) {⋯}
rest: function g(i, j, ...r) { return r.slice(i, j); } (instead of using arguments like a madman).
spread: let a = [0,1,2,3], o = new Something(...a);
proxies: let obj = Proxy.create(handler, proto). Long story short: ~ operator overloading with object-like elements.
weak map: let map = new WeakMap. Use it if you have circular references in it.
generators: function* gen() { yield 1; yield 2; } Actually, gen() returns ~ an object with a next() function property.
iterators: for (var [key, val] of items(x)) { alert(key + ',' + val); }. Iterators can be generators or proxies.
array and generator comprehension: [a+b for (a in A) for (b in B)] (array comprehension), (x for (x of generateValues()) if (x.color === 'blue')) (generator expression).
binary data: const Pixel = new StructType({x:uint32, y:uint32, color:Color}) (if Color is itself a StructType), new ArrayType(Pixel, 3).
class syntax, with extends, prototype, and super:
class Point extends Base {
constructor(x,y) {
super();
this[px] = x, this[py] = y;
this.r = function() { return Math.sqrt(x*x + y*y); }
}
get x() { return this[px]; }
get y() { return this[py]; }
proto_r() { return Math.sqrt(this[px] * this[px] +
this[py] * this[py]); }
equals(p) { return this[px] === p[px] &&
this[py] === p[py]; }
}modules:
module math {
export function sum(x, y) {
return x + y;
}
export var pi = 3.141593;
}import {sum, pi} from math;
alert(sum(pi,pi));quasis: multiline, substitution-ready strings with extensibility. `You are ${age} years old.`.
// The following regexp spans multiple lines.
re`line1: (words )*
line2: \w+`// It desugars to:
re({raw:'line1: (words )*\nline2: \w+',
cooked:'line1: (words )*\nline2: \w+'})