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JavaScript 1.5 to 2.0 (TomTom)
 

JavaScript 1.5 to 2.0 (TomTom)

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TomTom (May 2008).

TomTom (May 2008).

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    JavaScript 1.5 to 2.0 (TomTom) JavaScript 1.5 to 2.0 (TomTom) Presentation Transcript

    • JavaScript 1.5 to 2.0 John Resig (ejohn.org) Mozilla Corporation
    • The Big Picture ECMAScript 3 JavaScript 1.5 ActionScript 2 JScript Etc. SpiderMonkey AVM JScript Engine KJS (Apple) Rhino Opera
    • Jav aS 1999 crip t1 .5 Jav 2005 aS crip t1 .6 Jav 2006 aS crip t1 .7 Jav aS 2008 c Jav ript aS 1.8 cr ipt Ja Path to JavaScript 2 1.9 va 2009 Sc ri pt 2
    • The JavaScript Language Current: ✦ JavaScript 1.5 (Firefox 1, ES3) JavaScript 1.6 (Firefox 1.5) ✦ JavaScript 1.7 (Firefox 2) ✦ JavaScipt 1.8 (Firefox 3) ✦ JavaScript 1.9 (Firefox 3.1) ✦ JavaScript 2 (Firefox 4, ES4) ✦
    • JavaScript 1.5 Getters and Setters ✦ ✦ Extra power over properties ✦ Two powerful uses: ✦ Private data access ✦ Lazy-loading data var n = “John”; ✦ var obj = { get name(){ return n; }, set name(value){ n = value; } }; obj.name = “Ted”; obj.name == “Ted” // true
    • Getters and Setters var n = “John”; ✦ var obj = {}; obj.__defineGetter__(“name”, function(){ return n; }); obj.__defineSetter__(“name”, function(value){ n = value; }); obj.name = “Ted”; obj.name == “Ted”; // true obj.__lookupGetter__(“name”) ✦ // => function(){ return n; } // __lookupSetter__ too!
    • Lazy-Loading Data var pixelsDone; ✦ data.__defineGetter__(”pixels”, function(){ if ( pixelsDone ) return pixelsDone; pixelsDone = []; for ( var i = 0; i < pixels.length; i += 4 ){ pixelsDone.push( p.color(...) ); } return pixelsDone; }); obj.pixels[3] ✦
    • JavaScript 1.6 Array Extras ✦ ✦ indexOf / lastIndexOf [0,1,2].indexOf(1) == 1 ✦ every / filter / some [0,1,2].every(function(val){ return val > 0; }); // false ✦ map [0,1,2].map(function(val){return val + 1;}); // [1,2,3] ✦ forEach [0,1,2].forEach(function(val,index){});
    • JavaScript 1.7 Generators and Iterators ✦ ✦ Lazy-load data ✦ Database querying ✦ Threading http://www.neilmix.com/2007/02/07/ threading-in-javascript-17/
    • Generators and Iterators function fib() { ✦ var i = 0, j = 1; while (true) { yield i; var t = i; i = j; j += t; } } var g = fib(); for ( var i in g ) { document.write(i + “<br>n”); if ( i > 100 ) break; }
    • let Block-level statements ✦ for ( let i = 0; i < 10; i++ ) { } ✦ while ( true ) { let test = 5; } ✦ let (test = 5) { ✦ function stuff(){ return test; } } { let test = 5; ✦ { let test = 6; print(test);} print(test); }
    • Array Comprehension [i for ( let i = 0; i < 3; i++ )] ✦ // => [0, 1, 2] function range(begin, end) { ✦ for (let i = begin; i < end; ++i) { yield i; } } [i for each (i in range(0, 3))]
    • Destructuring var [newA, newB] = [a, b]; ✦ var newA = a, newB = b; ✦ [a, b] = [b, a] ✦ function test(){ return [0, 1]; } ✦ let [a, b] = test(); var [, c] = test(); var {name: name} = {name: “John”} ✦ name == “John” var {name} = {name: “John”} ✦
    • JavaScript 1.8 Mostly a bug fix release ✦ Expression Closures ✦ function(x){ return x * x; } function(x) x * x; Generator Expressions ✦ function val_iter(obj) { return (obj[x] for (x in obj)); } for ( let value in val_iter(obj) ) { ... }
    • reduce Great for summing or concating ✦ [x for ( x in 100 )] .reduce(function(a,b) a+b); [[...],[...]] ✦ .reduce(function(a,b){ a.concat(b);}, []) reduceRight ✦
    • JavaScript 1.9 Merge object properties: ✦ Object.extend( baseObj, otherObj ) Function.prototype.bind() ✦ fn.bind(someThis) “ string ”.trim() ✦ // => “string” mozilla.hashcode(someObj) ✦ // => 1234 (unique ID)
    • defineProperty Object.defineProperty(obj, name, value, ✦ types) var obj = {}; ✦ Object.defineProperty(obj, “name”, “John”, Object.NOT_WRITABLE | Object.NOT_DELETABLE); obj.name = “Test”; obj.name == “John”; delete obj.name obj.name == “John”;
    • JSON mozilla.JSON.parse(“{name:’John’}”) ✦ // => {name: ‘John’} mozilla.JSON.serialize({name:’John’}) ✦ // => “{name:’John’}”
    • Catchalls var props = {}; ✦ var obj = { test: true, get *(name){ return props[name]; }, set *(name, value){ props[name] = value; } } obj.__defineGetter_(“”, function(){}) ✦
    • JavaScript 2 Goals Backwards Compatible ✦ Suitable to developing large systems ✦ Allow for reusable libraries ✦ Merge previous efforts (ActionScript) ✦ Fix ECMAScript 3 bugs ✦ Keep it usable for small programs ✦
    • Features Classes and Interfaces ✦ Packages and Namespaces ✦ Type Annotations ✦ Strict Verification ✦ Optimization ✦ Syntax Shortcuts ✦ Iterators and Generators ✦ Self-hosting ✦
    • The Direction ECMAScript 4 JavaScript 2 ActionScript 4 JScript Etc. Screaming Tamarin KJS (Apple) Monkey Opera
    • Tamarin Tamarin ✦ ✦ New Virtual Machine from Adobe ✦ Perfect for ActionScript ✦ (a mutant cousin of JavaScript 2) The Three Monkeys: ✦ ✦ ActionMonkey ✦ ScreamingMonkey ✦ IronMonkey
    • Three Monkies ActionMonkey ✦ ✦ Integrating Tamarin into SpiderMonkey ✦ Powering Firefox 4 (?) + JavaScript 2 ScreamingMonkey ✦ ✦ Forcing Tamarin into Internet Explorer ✦ (Kicking and screaming?) IronMonkey ✦ ✦ Bringing Python + Ruby to Tamarin
    • Classes
    • Classes class Programmer { ✦ var name; var city = “Boston, MA”; const interest = “computers”; function work() {} } var p = new Programmer; ✦ p.name = “John”; p.work(); p.work.apply( someotherp ); p.interest = “science”; // Error
    • Dynamic Classes dynamic class Programmer { ✦ var name; var city = “Boston, MA”; const interest = “computers”; function work() {} } var p = new Programmer; ✦ p.lastName = “Resig”; for ( var i in p ) alert( i ); // alert( “Resig” );
    • Getters and Setters class Programmer { ✦ var _name; function get name(){ return _name; } function set name(value){ _name = value + “ Resig”; } } var p = new Programmer; ✦ p.name = “John”; alert( p.name ); // “John Resig”
    • Catch-Alls dynamic class Programmer { ✦ meta function get(name) { ... } meta function set(name, value) { alert(“Setting “ + name + “ to “ + value); } } var p = new Programmer ✦ p.name = “John”; // alert(“Setting name to John”);
    • Inheritance class Artist { ✦ function draw() { alert(“Drawing!”); } } class Designer extends Artist { override function draw() { alert(“Designing!”); } } var d = new Designer ✦ d.draw(); // alert(“Designing!”);
    • Inheritance (cont.) ‘final’ methods can’t be overriden ✦ class Artist { ✦ final function draw() {alert(“Drawing!”);} } class Designer extends Artist { // ERROR: Can’t override draw! override function draw() { alert(“Designing!”); } }
    • Inheritance (cont.) ‘final’ classes can’t be inherited from ✦ final class Artist { ✦ function draw() { alert(“Drawing!”); } } // ERROR: Can’t inherit from Artist class Designer extends Artist { override function draw() { alert(“Designing!”); } }
    • Metaclass Provide global functions and properties on ✦ a class object class Users { ✦ static function find( name ) { // ... } } Users.find( “John” ); ✦
    • Interfaces Verify that a class implements another ✦ class Artist { ✦ function draw(); } class Designer implements Artist { function draw() { alert(“Designing!”); } } if ( Designer is Artist ) ✦ alert(“Designers are Artists!”);
    • Types
    • Types Types are broken down into: ✦ ✦ string ✦ double (ECMAScript 3-style Number) ✦ boolean
    • Type Annotations var name : string = “John”; ✦ let x : double = 5.3; ✦ function stuff( x: string, obj: Object ) : ✦ boolean {}
    • Function Types Only return specific types: ✦ function isValid() : boolean { } Only be used on certain objects types: ✦ function every( this: Array ) { for ( var i = 0; i < this.length; i++ ) alert( this[i] ); } every.call( [0,1,2] ); // alert(0); alert(1); alert(2); every.call({a: “b”}); // ERROR
    • Rest Arguments function stuff( name, ...values ){ ✦ alert( values.length ); } stuff( “John”, 1, 2, 3, 4 ); ✦ // alert( 4 ); function stuff( name : string, ...values : [double] ) : void ✦ { alert( values.length ); } var array = [1,2,3,4]; ✦ stuff( “John”, ...array );
    • Union and Any Types var test : (string, double) = “test”; ✦ test = 3; test = {}; // ERROR These are equivalent: ✦ ✦ var test : * = “test”; ✦ var test = “test”;
    • Type Definitions type Point = { x: double, y: double }; ✦ var p : Point = { x: 3.0, y: 24.0 }; ✦
    • Nullability Prevent variables from accepting null ✦ values var name : * = “John”; ✦ var name : string! = “John”; ✦ name = “Ted”; name = null; // ERROR function test( name: string? ) { ✦ alert( name ); }
    • Initialization class User { ✦ var name : string!; // Must be initialized function User( n ) : name = n { // ... } }
    • “like” type Point = { x: double, y: double }; ✦ if ( { x: 3, y: 5 } like Point ) ✦ alert( “That looks like a point to me!” ); if ( !({ x: 3 } like Point) ) ✦ alert( “Not a point!” ); // Loop over array-like things: ✦ function every( a: like { length: double } ) { for ( var i = 0; i < a.length; i++ ) alert( a[i] ); }
    • Parameterized Types var m: Map.<string, *>; ✦ class Point.<T> { ✦ var x: T, y: T; } var p = new Point.<double>; ✦ p.x = 3.0; p.y = 5.0;
    • Structure
    • Namespaces namespace extra = “extra”; ✦ Pre-defined namespaces: ✦ ✦ __ES4__ ✦ intrinsic ✦ iterator ✦ meta Namespaced variables: ✦ iteration::StopIteration intrinsic::readFile
    • Multimethods generic function intersect(s1, s2); ✦ generic function intersect(s1: Shape, s2: Shape ) { // ... } generic function intersect(s1: Rect, s2: Rect ) { // ... } generic function test(a: Object?, b... ✦ generic function test(a: Object! ✦
    • Iteration class Fib { ✦ private var a=0, b=1; iterator function get(deep:boolean = false) : IteratorType.<double> this public function next(): double { if ( b > 100 ) throw iterator::StopIteration; [a,b] = [b,a+b]; return a; } } for ( let i in new Fib ) ✦ alert( i );
    • For .. Each For each loops through values ✦ let s = “”; ✦ for each ( let n in [“a”,”b”,”c”] ) s += n; alert(s); // “abc”
    • Self-Hosting
    • Map.es The reference implementation’s classes are ✦ written in ECMAScript package ✦ { use namespace intrinsic; use default namespace public; intrinsic class Map.<K,V> { static const length = 2; function Map(equals=intrinsic::===, hashcode=intrinsic::hashcode) : equals = equals , hashcode = hashcode , element_count = 0 { } // ... }
    • More Info ECMAScript 4 Progress: ✦ http://spreadsheets.google.com/ccc?key=pFIHldY_CkszsFxMkQOReAQ&hl=en ECMAScript 4 White Paper Overview: ✦ http://www.ecmascript.org/es4/spec/overview.pdf Blogging: ✦ http://ejohn.org/