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JavaScript 1.5 to 2.0 (TomTom)

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JavaScript 1.5 to 2.0 (TomTom)

  1. JavaScript 1.5 to 2.0 John Resig (ejohn.org) Mozilla Corporation
  2. The Big Picture ECMAScript 3 JavaScript 1.5 ActionScript 2 JScript Etc. SpiderMonkey AVM JScript Engine KJS (Apple) Rhino Opera
  3. 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
  4. 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) ✦
  5. 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
  6. 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!
  7. 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] ✦
  8. 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){});
  9. JavaScript 1.7 Generators and Iterators ✦ ✦ Lazy-load data ✦ Database querying ✦ Threading http://www.neilmix.com/2007/02/07/ threading-in-javascript-17/
  10. 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; }
  11. 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); }
  12. 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))]
  13. 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”} ✦
  14. 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) ) { ... }
  15. 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 ✦
  16. 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)
  17. 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”;
  18. JSON mozilla.JSON.parse(“{name:’John’}”) ✦ // => {name: ‘John’} mozilla.JSON.serialize({name:’John’}) ✦ // => “{name:’John’}”
  19. Catchalls var props = {}; ✦ var obj = { test: true, get *(name){ return props[name]; }, set *(name, value){ props[name] = value; } } obj.__defineGetter_(“”, function(){}) ✦
  20. 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 ✦
  21. Features Classes and Interfaces ✦ Packages and Namespaces ✦ Type Annotations ✦ Strict Verification ✦ Optimization ✦ Syntax Shortcuts ✦ Iterators and Generators ✦ Self-hosting ✦
  22. The Direction ECMAScript 4 JavaScript 2 ActionScript 4 JScript Etc. Screaming Tamarin KJS (Apple) Monkey Opera
  23. Tamarin Tamarin ✦ ✦ New Virtual Machine from Adobe ✦ Perfect for ActionScript ✦ (a mutant cousin of JavaScript 2) The Three Monkeys: ✦ ✦ ActionMonkey ✦ ScreamingMonkey ✦ IronMonkey
  24. 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
  25. Classes
  26. 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
  27. 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” );
  28. 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”
  29. 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”);
  30. Inheritance class Artist { ✦ function draw() { alert(“Drawing!”); } } class Designer extends Artist { override function draw() { alert(“Designing!”); } } var d = new Designer ✦ d.draw(); // alert(“Designing!”);
  31. 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!”); } }
  32. 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!”); } }
  33. Metaclass Provide global functions and properties on ✦ a class object class Users { ✦ static function find( name ) { // ... } } Users.find( “John” ); ✦
  34. 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!”);
  35. Types
  36. Types Types are broken down into: ✦ ✦ string ✦ double (ECMAScript 3-style Number) ✦ boolean
  37. Type Annotations var name : string = “John”; ✦ let x : double = 5.3; ✦ function stuff( x: string, obj: Object ) : ✦ boolean {}
  38. 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
  39. 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 );
  40. Union and Any Types var test : (string, double) = “test”; ✦ test = 3; test = {}; // ERROR These are equivalent: ✦ ✦ var test : * = “test”; ✦ var test = “test”;
  41. Type Definitions type Point = { x: double, y: double }; ✦ var p : Point = { x: 3.0, y: 24.0 }; ✦
  42. 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 ); }
  43. Initialization class User { ✦ var name : string!; // Must be initialized function User( n ) : name = n { // ... } }
  44. “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] ); }
  45. 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;
  46. Structure
  47. Namespaces namespace extra = “extra”; ✦ Pre-defined namespaces: ✦ ✦ __ES4__ ✦ intrinsic ✦ iterator ✦ meta Namespaced variables: ✦ iteration::StopIteration intrinsic::readFile
  48. 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! ✦
  49. 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 );
  50. For .. Each For each loops through values ✦ let s = “”; ✦ for each ( let n in [“a”,”b”,”c”] ) s += n; alert(s); // “abc”
  51. Self-Hosting
  52. 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 { } // ... }
  53. 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/

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