ECMAScript, what's all the fuss about ?

ECMAScript, what's all the fuss about ?

ECMAScript, what's all the fuss about ?

ECMAScript, what's all the fuss about ?

Now, let's get into the interesting stuff

But first...

some jokes

Strict Mode

• Makes it easier to write "secure" JavaScript.
• Changes previously accepted "bad syntax" into real errors.

// Non-strict code...

(function(){
   "use strict";
   
   // Define your library strictly...
})();
     
// Non-strict code..

Accessors

var person = {
    firstName: 'Jimmy',
    lastName: 'Smith',
    get fullName() {
       return this.firstName + ' ' + this.lastName;
    },
    set fullName (name) {
       var words = name.toString().split(' ');
       this.firstName = words[0] || '';
       this.lastName = words[1] || '';
    }
}

person.fullName = 'Jack Franklin';
console.log(person.firstName); // Jack
console.log(person.lastName) // Franklin

Syntactic Changes

• You can use reserved words (such as new and function) after the dot operator and as unquoted property keys in object literals.
• Trailing commas in object literals and array literals are legal.
• String literals can span multiple lines if you escape the end of the line via a backslash.

/* Reserved keywords */
var person = {
    new: 'hi'
};
person.new //hi

/* Trailing comma's */
var obj = {
        first: 'Jane',
        last: 'Doe',
        age: 40,  // trailing comma
    };

var arr = [ 'a', 'b', 'c', ];
arr //[ 'a', 'b', 'c' ]
arr.length //3

/* String literals */
var multiStr = "This is the first line \
	This is the second line \
	This is more...";

New Functionality in the Standard Library

• Object.create()
• Object.getPrototypeOf()
• Object.seal()
• Object.freeze()
• String.prototype.trim()
• Array.isArray()
• Array.prototype.forEach()
• Array.prototype.indexOf()
• Date.now()
• JSON.parse()
• JSON.stringify()

ECMAScript 5 brought several additions to JavaScript’s standard library. Some (important) examples are listed below:

Arrows

Classes

Enhanced Object Literals

Template Strings

Destructuring

Default + ...

Let + Const

Iterables and iterators

Generators

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));

// otherApp.js
import {sum, pi} from "lib/math";
alert("2π = " + sum(pi, pi));

//Language-level support for modules for component definition. 
//Codifies patterns from popular JavaScript module loaders (AMD, CommonJS).

Module Loaders

// Dynamic loading – ‘System’ is default loader
System.import('lib/math').then(function(m) {
  alert("2π = " + m.sum(m.pi, m.pi));
});

// Create execution sandboxes – new Loaders
var loader = new Loader({
  global: fixup(window) // replace ‘console.log’
});
loader.eval("console.log('hello world!');");

Module loaders support:

    Dynamic loading
    State isolation
    Global namespace isolation
    Compilation hooks
    Nested virtualization

Map + Set + WeakMap + WeakSet

Proxies

Math + Number + String + Array + Object APIs

Number.EPSILON
Number.isInteger(Infinity) // false
Number.isNaN("NaN") // false

Math.acosh(3) // 1.762747174039086
Math.hypot(3, 4) // 5
Math.imul(Math.pow(2, 32) - 1, Math.pow(2, 32) - 2) // 2

"abcde".includes("cd") // true
"abc".repeat(3) // "abcabcabc"

Array.from(document.querySelectorAll('*')) // Returns a real Array
Array.of(1, 2, 3) // Similar to new Array(...), but without special one-arg behavior
[0, 0, 0].fill(7, 1) // [0,7,7]
[1, 2, 3].find(x => x == 3) // 3
[1, 2, 3].findIndex(x => x == 2) // 1
[1, 2, 3, 4, 5].copyWithin(3, 0) // [1, 2, 3, 1, 2]
["a", "b", "c"].entries() // iterator [0, "a"], [1,"b"], [2,"c"]
["a", "b", "c"].keys() // iterator 0, 1, 2
["a", "b", "c"].values() // iterator "a", "b", "c"

Object.assign(Point, { origin: new Point(0,0) })

Promises

function timeout(duration = 0) {
    return new Promise((resolve, reject) => {
        setTimeout(resolve, duration);
    })
}

var p = timeout(1000).then(() => {
    return timeout(2000);
}).then(() => {
    throw new Error("hmm");
}).catch(err => {
    return Promise.all([timeout(100), timeout(200)]);
})