JavaScript ES6

Welcoming JavaScript
ES6
Top 10 reasons why you should be using
ES6, number 7 will bring you tears of joy!
(Click Here)
@leojh

● I work at Third Wave
● We are right here at Cendyn Spaces
● We build custom business software
● We’re doing a lot of JavaScript development
● We’re AGILE
● We’re here if you need us!
● http://thirdwave.it

What is ES6?
● New ECMA standard bringing modern
features and cleaner syntax to JavaScript
● Scheduled for official release later in 2015
● Mozilla Firefox leading in browser
adoptability
● Standard mostly completed
● You can begin using it TODAY!

class IntArrayAction
{
constructor(ints) {
this.ints = ints;
}
doSomethingOnInts(action) {
for (var i of this.ints) {
action(i);
}
}
}
var instance = new IntArrayAction([1,2,3,4,5]);
instance.doSomethingOnInts((i) => console.log(i));

class IntArrayAction
{
constructor(ints) {
this.ints = ints;
}
doSomethingOnInts(action) {
for (var i of this.ints) {
action(i);
}
}
}
var instance = new IntArrayAction([1,2,3,4,5]);
instance.doSomethingOnInts((i) => console.log(i));
class keyword
constructor keyword
iterator
lambda

Some of the Features
Classes
Iterators
Lambdas
Modules
String Interpolation
Unicode
Set & Map Types
Parameter defaults
Lots of Syntax Sugar
…
And much more

Classes
Structure code in classes instead of object
literals or “function objects”
Inheritance through extends keyword and call
parent members through super(...)
Include class members through static
keyword (like in C#)

Classes
class SkinnedMesh extends THREE.Mesh {
constructor(geometry, materials) {
super(geometry, materials);
this.idMatrix = SkinnedMesh.defaultMatrix();
this.bones = [];
this.boneMatrices = [];
//...
}
update(camera) {
//...
super.update();
}
static defaultMatrix() {
return new THREE.Matrix4();
}
}

● Declare using ` (backtick) operator
● Lets you put statements inside of strings
var name = ‘Slim Shady’
var greeting = `Hi, my name is: ${name}!`
● Lets you create multi-line string literals
var multiLine = `Line 1
Line 2`

// Basic literal string creation
`In JavaScript "n" is a line-feed.`
// Multiline strings
`In JavaScript this is
not legal.`
// Interpolate variable bindings
var name = "Bob", time = "today";
`Hello ${name}, how are you ${time}?`
// Construct an HTTP request prefix is used to interpret the replacements and construction
GET`http://foo.org/bar?a=${a}&b=${b}
Content-Type: application/json
X-Credentials: ${credentials}
{ "foo": ${foo},
"bar": ${bar}}`(myOnReadyStateChangeHandler);

Sets & Maps Types
● A real Map/Dictionary type (finally!)
○ Will map a key to a value
● Provides Weak Implementations
○ To map object keys to values
○ The contents may be garbage collected if the object
keys are removed from memory

Sets & Map Types
// Sets
var s = new Set();
s.add("hello").add("goodbye").add("hello");
s.size === 2;
s.has("hello") === true;
// Maps
var m = new Map();
m.set("hello", 42);
m.set(s, 34);
m.get(s) == 34;
// Weak Maps
var wm = new WeakMap();
wm.set(s, { extra: 42 });
wm.size === undefined
// Weak Sets
var ws = new WeakSet();
ws.add({ data: 42 });
// Because the added object has no other references, it will not be held in the set

Iterators
● Will let you create iterable types like
IEnumerable (C#) or Iterable (Java)
● For Each Loops now available (finally!)
○ If you are using for..in to iterate arrays, you’re doing
it wrong!

Iterators
let fibonacci = {
[Symbol.iterator]() {
let pre = 0, cur = 1;
return {
next() {
[pre, cur] = [cur, pre + cur];
return { done: false, value: cur }
}
}
}
}
for (var n of fibonacci) {
// truncate the sequence at 1000
if (n > 1000)
break;
console.log(n);
}

=> (lambdas λ and functions)
● Shorthand for function()
● Similar syntax to C#
○ No parentheses for single argument
○ No return keyword necessary for single statement
● Will keep reference to outer this for you
○ No need to: var self = this;
● Closure

=> (lambdas and functions)
// Expression bodies
var odds = evens.map(v => v + 1);
var nums = evens.map((v, i) => v + i);
// Statement bodies
nums.forEach(v => {
if (v % 5 === 0)
fives.push(v);
});
// Lexical this
var bob = {
_name: "Bob",
_friends: [],
printFriends() {
this._friends.forEach(f =>
console.log(this._name + " knows " + f));
}
}

Let Block Scope
● New keyword let for creating block scope
● You should probably stop using var and use
let instead (do as I say, not as I do)
● var = function scope
let = block scope
● BONUS: We have a const keyword
(finally!)

Modules
● Arguably the most important feature
● A legitimate way to make code reusable
(finally!)
● Export a module/library
● Import the module/library when needed
● Transpiles to CommonJS or RequireJS
● Provides Static Analysis for dependencies

Modules
// lib/math.js
export function sum(x, y) {
return x + y;
}
export var pi = 3.141593;
// app.js
import * as math from "lib/math";
alert("2π = " + math.sum(math.pi, math.pi));

Learn ES6 in 24 hours!
● Best ES6 resource by
far is babel.js (https://babeljs.io)
● It is currently the leading
ES6 transpiler
● Contains a lot of great training material
● Has a live ES6 editor
● Definitely visit babel.js

Begin using ES6 today!
If you’re using:
● ember-cli - start typing ES6 code
● react-js - use react-tools
● AngularJS - looks complicated, but then again you’re
using Angular so you’re used to it
● node - use babel-node tool
● Plain old javascript: use broccoli-js

JavaScript ES6

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