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JavaScript
From birth to closure
Yeah, nothing
Brendan Eich
Brendan Eich
What is JavaScript?
• Developed by Brendan Eich 1995
• Initially called Mocha, then LiveScript
• First day of light in a beta of Netscape 2
in December 1995
• IE followed suit with JScript in 1996
JavaScript - From Birth To Closure
JavaScript - From Birth To Closure
“You’re number one!”
Has NOTHING to do
with Java!
• JavaScript is one of the world’s most
popular programming languages
• One interpreter on every machine
• ECMAScript standardizing - Fifth edition
• Web browsers becoming much faster
JavaScript - From Birth To Closure
SunSpider test
Douglas Crockford
Douglas Crockford
• JSON
• JSLint
• JSMin
JavaScript - From Birth To Closure
JavaScript basics
Variable declaration:
var benAffleck = ”Actor”;
Function declaration:
function benQuote () {
! return "Rumors about me?
Calista Flockhart, Pam
Anderson, and Matt Damon.
That's who I'm dating.";
}
Conditionals
• If
• Switch
• Shorthand assignment
• Ternary operators
function makeMovie (withLivTyler) {
! var nice = withLivTyler || false;
}
(datedJLo)? "Lucky guy!" : "No?";
Comparison operators
• =	

 Assignment
• ==	

 Equality
• === Identity
// Assignment
var bestFriend = "Matt Damon";
// Equality
if (5 == "5") {
! // true
}
// Identity
if (5 === "5") {
! // false
}
// Short-circuit logic
if (true || false)
if (false && true)
// Makes this code safe
if (obj && obj.property)
// Short-circuit logic
if (true || false)
if (false && true)
// Makes this code safe
if (obj && obj.property)
Type coercion
// true
5 == "5"
// 123
"1" + 2 + 3;
// 6, manual type conversion
parseInt("1", 10) + 2 + 3;
null == undefined == 0 ==
false == ""
• Not really, but sort of
• Rather “truthy” or “falsy”
var a = null;
var b; // undefined
var c = 0;
var d = false;
var e = "";
if (a) // false
if (b) // false
if (c) // false
if (d) // false
if (e) // false
JavaScript data types
• string
• number
• boolean
• null
• undefined
• Object
Types of Object include:
• function
• Array
• Date
• RegExp
Checking type
typeof return values:
• string
• number
• boolean
• function
• object
• undefined
typeof fanClub // "undefined"
var title = "Armageddon";
typeof title // Equals "string"
var age = 37;
typeof age // Equals "number"
function anotherQuote () {
! return "If I ever woke up
with a dead hooker in my
hotel room, Matt would be
the first person I'd call.";
}
typeof anotherQuote; //"function"
var obj = {};
typeof obj = // "object"
var arr = ["B", "E", "N"];
typeof arr // "object"
var obj = {};
typeof obj = // "object"
var arr = ["B", "E", "N"];
typeof arr // "object" ?!
Using instanceof
obj instanceof Array // false
arr instanceof Array // true
Functions
Procedural
function notAHit () {
! return "Gigli";
}
Functions as variables
var wroteScript = function () {
! return "Good Will Hunting";
};
wroteScript();
Anonymous
document.onmousemove = function (evt) {
alert(evt.pageX);
};
Self-invoking
(function () {
! var dogma = "Shot in 1999";
})();
Self-invoking
(function () {
! var dogma = "Shot in 1999";
})();
Function arguments
• Any argument can be omitted
• Any argument can be added
• No overloading
• The arguments collection
function concat (a, b, c) {
! return a + b + c;
}
concat(1, 2, 3); // 6
concat(1, 2); // NaN
• The arguments collection
• Property: arguments.length
• NOT an array
function concat () {
! var sum = 0,
l = arguments.length;
! for (var i=0; i<l; i++) {
! ! sum += arguments[i];
! }
! return sum;
}
concat(1, 2, 3); // 6
concat(1, 2); // 3
concat(1, 2, 7, 11, 5); // 26
Objects
function Ben () {
! this.name = "Ben Affleck";
! this.gotAnOscar = true;
};
var ben = new Ben();
alert(ben.gotAnOscar); // true
Object constructor
var ben = {
! name : "Ben Affleck",
! gotAnOscar : true
};
alert(ben.name); // "Ben Affleck"
Object literal
Different syntax, same thing:
ben["arms"] = 2;
ben.arms = 2;
Different syntax, same thing:
ben["arms"] = 2;
ben.arms = 2;
For any object:
var ben = {};
ben[1972] = "Year of birth";
ben["born"] = 1972;
ben[true] = false;
var regEx = new RegExp;
regEx[3] = "I can do this?";
var goodMovie = {
! title : "Good Will Hunting",
! year : 1997
};
for (var item in goodMovie) {
! alert(item + ": " + goodMovie[item]);
}
var goodMovie = {
! title : "Good Will Hunting",
! year : 1997
};
// Check returns true
if ("year" in goodMovie) {
! alert(goodMovie.year);
}
Inheritance
• Prototype-based inheritance
• Not class-based
• The prototype chain checks itself first
• It then goes to the parent, parent’s parent
etc...
function Being () {
! this.living = true;
}
Being.prototype.greet = function () {
! return "Hello!";
};
function Ben () {
! this.talks = true;
}
Ben.prototype = new Being;
Ben.prototype.saySomething = function () {
! return "I feel like fame is wasted on me.";
};
// Create an instance
var ben = new Ben();
// Returns "I feel like fame is wasted on me."
ben.saySomething();
// Returns "Hello!", inherited
// from the Being object
ben.greet();
Checking for the greet() method in this order:
• ben instance
• Ben prototype
• Being prototype
• Object prototype
• Simple JavaScript Inheritance
• A Base Class for JavaScript Inheritance
• Defining classes and inheritance
Class-based mimicking
• It’s native, i.e. no dependencies
• Freedom of style and version
• Easy readability
• Code handover
Why prototype syntax
“I have been writing JavaScript for 8 years
now, and I have never once found need to
use an uber function...
...I now see my early attempts to support the
classical model in JavaScript as a mistake.”
- Douglas Crockford
Why prototype syntax
Scope
• Scope refers to where variables and
functions are accessible
• In what context something is being
executed
• Basically, global or local
• Variables have function scope
• Functions have the same scope as variables
// Global
var likesToPlay = "Poker";
function getGame () {
! // Local
! var likesToPlay = "Hold ‘em";
! // Global
! playOnline = true;
! return likesToPlay;
! // Returns "Hold ‘em"
}
function playPoker (money) {
! if (money) {
! ! var willPlay = true;
! }
! // Perfectly valid
! return willPlay;
}
function global () {
! return "Access anywhere";
}
function outer () {
! function inner () {
! ! return "Inner";
! }
! return inner();
}
outer(); // Accessible
inner(); // Not accessible
“Global scope is like a public toilet.
You can’t avoid going in there. But
try to limit your contact with
surfaces when you do.”
- Dmitry Baranovskiy, Raphaël JS
library
Polluting the global
namespace
Function scope
• Run a function in a certain context
• The call and apply methods
• Defined for all functions
function docReady () {
! alert(this);
! // this is the window object
}
window.onload = docReady;
function setName (name) {
! this.name = name;
! // document.name === "Bennifer"
}
document.onclick = function () {
! setName.call(document, "Bennifer");
};
function setName (name) {
! this.name = name;
! // document.name === "Bennifer"
}
document.onclick = function () {
! setName.call(document, "Bennifer");
};
function setNames () {
! this.firstName = arguments[0];
! this.lastName = arguments[1];
// document.firstName === “Ben”
// document.lastName === “Affleck”
}
function callSetNames () {
! setNames.apply(document, arguments);
};
callSetNames("Ben", "Affleck");
function setNames () {
! this.firstName = arguments[0];
! this.lastName = arguments[1];
// document.firstName === “Ben”
// document.lastName === “Affleck”
}
function callSetNames () {
! setNames.apply(document, arguments);
};
callSetNames("Ben", "Affleck");
Closures
JavaScript - From Birth To Closure
JavaScript - From Birth To Closure
JavaScript - From Birth To Closure
JavaScript - From Birth To Closure
• Closures are expressions, usually functions,
which can work with variables set within a
certain context
• Inner functions referring to local variables
of its outer function create closures
function add (x) {
! return function (y) {
! ! return x + y;
! };
}
var add5 = add(5);
var no7 = add5(2); // Equals 7
“Right...What?!”
function add (x) {
! return function (y) {
! ! return x + y;
! };
}
var add5 = add(5);
// How JavaScript sees it
var add5 = function (y) {
! return 5 + y;
}
function add (x) {
! return function (y) {
! ! return x + y;
! };
}
var add5 = add(5);
// How JavaScript sees it
var add5 = function (y) {
! return 5 + y;
}
function addLinks () {
! for (var i=0, link; i<5; i++) {
! ! link = document.createElement("a");
! ! link.innerHTML = "Link " + i;
! ! link.onclick = function () {
! ! ! alert(i);
! ! };
! ! document.body.appendChild(link);
! }
}
window.onload = addLinks;
function addLinks () {
! for (var i=0, link; i<5; i++) {
! ! link = document.createElement("a");
! ! link.innerHTML = "Link " + i;
! ! link.onclick = function () {
! ! ! alert(i);
! ! };
! ! document.body.appendChild(link);
! }
}
window.onload = addLinks;
! ! link.onclick = function () {
! ! ! alert(i);
! ! };
function addLinks () {
! for (var i=0, link; i<5; i++) {
! ! link = document.createElement("a");
! ! link.innerHTML = "Link " + i;
! ! link.onclick = function (num) {
! ! ! return function () {
! ! ! ! alert(num);
! ! ! };
! ! }(i);
! ! document.body.appendChild(link);
! }
}
window.onload = addLinks;
function addLinks () {
! for (var i=0, link; i<5; i++) {
! ! link = document.createElement("a");
! ! link.innerHTML = "Link " + i;
! ! link.onclick = function (num) {
! ! ! return function () {
! ! ! ! alert(num);
! ! ! };
! ! }(i);
! ! document.body.appendChild(link);
! }
}
window.onload = addLinks;
! ! link.onclick = function (num) {
! ! ! return function () {
! ! ! ! alert(num);
! ! ! };
! ! }(i);
function addLinks () {
! for (var i=0, link; i<5; i++) {
! ! link = document.createElement("a");
! ! link.innerHTML = "Link " + i;
! ! link.onclick = function (num) {
! ! ! return function () {
! ! ! ! alert(num);
! ! ! };
! ! }(i);
! ! document.body.appendChild(link);
! }
}
window.onload = addLinks;
! ! link.onclick = function (num) {
! ! ! return function () {
! ! ! ! alert(num);
! ! ! };
! ! }(i);
function addLinks () {
! for (var i=0, link; i<5; i++) {
! ! link = document.createElement("a");
! ! link.innerHTML = "Link " + i;
! ! link.onclick = function (num) {
! ! ! return function () {
! ! ! ! alert(num);
! ! ! };
! ! }(i);
! ! document.body.appendChild(link);
! }
}
window.onload = addLinks;
! ! link.onclick = function (num) {
! ! ! return function () {
! ! ! ! alert(num);
! ! ! };
! ! }(i);
function addLinks () {
! for (var i=0, link; i<5; i++) {
! ! link = document.createElement("a");
! ! link.innerHTML = "Link " + i;
! ! link.onclick = function (num) {
! ! ! return function () {
! ! ! ! alert(num);
! ! ! };
! ! }(i);
! ! document.body.appendChild(link);
! }
}
window.onload = addLinks;
! ! link.onclick = function (num) {
! ! ! return function () {
! ! ! ! alert(num);
! ! ! };
! ! }(i);
Yahoo JavaScript
Module Pattern
• Origins from Douglas Crockford
• Singleton pattern
• Offers private and public members
var goneBabyGone = function () {
! // Private members
! var movieTitle = "Gone Baby Gone",
isDirectedByBen = true;
!
! // Public members
! return {
! ! title : function () {
! ! ! return movieTitle;
! ! },
! !
! ! directedByBen : function () {
! ! ! return isDirectedByBen;
! ! }
! };
}();
var goneBabyGone = function () {
! // Private members
! var movieTitle = "Gone Baby Gone",
isDirectedByBen = true;
!
! // Public members
! return {
! ! title : function () {
! ! ! return movieTitle;
! ! },
! !
! ! directedByBen : function () {
! ! ! return isDirectedByBen;
! ! }
! };
}();
var goneBabyGone = function () {
! // Private members
! var movieTitle = "Gone Baby Gone",
isDirectedByBen = true;
!
! // Public members
! return {
! ! title : function () {
! ! ! return movieTitle;
! ! },
! !
! ! directedByBen : function () {
! ! ! return isDirectedByBen;
! ! }
! };
}();
var goneBabyGone = function () {
! // Private members
! var movieTitle = "Gone Baby Gone",
isDirectedByBen = true,
! ! title = function () {
! ! ! return movieTitle;
! ! },
! !
! ! directedByBen = function () {
! ! ! return isDirectedByBen;
! ! };
!
! // Public members
! return {
title : title,
directedByBen : directedByBen
! };
}();
Namespacing
• Avoiding global variables
• Code structure
• Extending, but not necessarily inheriting
// Create a Ben object
var Ben = {};
// Set functionality
Ben.Director = function () {
! var noOfMovies = 4;
! return {
! ! movies : function () {
! ! ! return noOfMovies;
! ! }
! };
}();
// Assertion
if (typeof Ben === "undefined") {
! Ben = {};
}
Ben.Actor = function () {
! var noOfMovies = 51;
! return {
! ! actAndDirectorCount : function () {
! ! ! return noOfMovies + " as actor & "
+ Ben.Director.movies.call(this)
+ " as Director";
! ! }
! };
}();
Sugar & spice
It’s awfully nice!
• Sugaring
• Currying
// A little sugar
String.prototype.trim = function () {
! return this.replace(/^s*|s*$/g, "");
};
var monkey = " Monkey ";
monkey.trim(); //"Monkey"
// Currying
function add () {
! var sum = 0;
! for (var i=0, il=arguments.length; i<il; i++) {
! ! sum += arguments[i];
! };
! return sum;
}
// Currying (continued) - Currying method by Crockford!
!
Function.prototype.curry = function () {
! var slice = Array.prototype.slice,
! ! args = slice.apply(arguments),
! ! that = this;
! return function () {
! ! ! return that.apply(
! ! ! ! null, args.concat(slice.apply(arguments))
! ! ! );
! };
}
var add8 = add.curry(5, 3);
alert(add8(1, 3, 7)); // 19
// Currying (continued) - Currying method by Crockford!
!
Function.prototype.curry = function () {
! var slice = Array.prototype.slice,
! ! args = slice.apply(arguments),
! ! that = this;
! return function () {
! ! ! return that.apply(
! ! ! ! null, args.concat(slice.apply(arguments))
! ! ! );
! };
}
var add8 = add.curry(5, 3);
alert(add8(1, 3, 7)); // 19
// Currying (continued) - Currying method by Crockford!
!
Function.prototype.curry = function () {
! var slice = Array.prototype.slice,
! ! args = slice.apply(arguments),
! ! that = this;
! return function () {
! ! ! return that.apply(
! ! ! ! null, args.concat(slice.apply(arguments))
! ! ! );
! };
}
var add8 = add.curry(5, 3);
alert(add8(1, 3, 7)); // 19
// Currying (continued) - Currying method by Crockford!
!
Function.prototype.curry = function () {
! var slice = Array.prototype.slice,
! ! args = slice.apply(arguments),
! ! that = this;
! return function () {
! ! ! return that.apply(
! ! ! ! null, args.concat(slice.apply(arguments))
! ! ! );
! };
}
var add8 = add.curry(5, 3);
alert(add8(1, 3, 7)); // 19
// Currying (continued) - Currying method by Crockford!
!
Function.prototype.curry = function () {
! var slice = Array.prototype.slice,
! ! args = slice.apply(arguments),
! ! that = this;
! return function () {
! ! ! return that.apply(
! ! ! ! null, args.concat(slice.apply(arguments))
! ! ! );
! };
}
var add8 = add.curry(5, 3);
alert(add8(1, 3, 7)); // 19
// Currying (continued) - Currying method by Crockford!
!
Function.prototype.curry = function () {
! var slice = Array.prototype.slice,
! ! args = slice.apply(arguments),
! ! that = this;
! return function () {
! ! ! return that.apply(
! ! ! ! null, args.concat(slice.apply(arguments))
! ! ! );
! };
}
var add8 = add.curry(5, 3);
alert(add8(1, 3, 7)); // 19
Syntax
recommendations
• No real standard, only best practices
• Recommended tool: JSLint
Embrace JavaScript
• Embrace JavaScript
• Don’t try to make it into Java, C or any
other language
• Learn to love it and its dynamic, loose and
prototypical nature
This is how we roll
Robert Nyman
robertnyman.com/speaking/
robert@robertnyman.com
Twitter: @robertnyman
Pictures:
Brendan - http://www.flickr.com/photos/mollyeh11/279367481/
Yoda - http://buzzybeegirl.files.wordpress.com/2008/12/yoda-400x3001.jpg
Twitter - http://twitter.com/manssandstrom/status/1528315581
Gmail - http://www.flickr.com/photos/webber/71748774/
Slow - http://www.feministing.com/archives/012345.html
Crockford - http://www.flickr.com/photos/charliebrewer/2897862701/
Obi-Wan - http://enterthecircle.files.wordpress.com/2009/01/obi-wan-kenobi-01-large.jpg
Ben Affleck - http://www.flickr.com/photos/sasy/3993866442/
Squat toilet - http://www.flickr.com/photos/35034350906@N01/4080372999
Cuddling bears - http://www.nogg.se/blogg.asp?intShowMenu=a2&idHomepage=6951&idBloggCategory=6162
Winnie The Pooh and friends - http://mammacarola.blogg.se/2009/april/
IEVoodoo Doll - http://nexus404.com/Blog/2007/10/26/make-your-own-internet-explorer-voodoo-doll-a-step-by-step-guide/
Ben Affleck confused - http://cdn.buzznet.com/assets/imgx/4/9/0/5/8/orig-49058.jpg

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JavaScript - From Birth To Closure

  • 6. • Developed by Brendan Eich 1995 • Initially called Mocha, then LiveScript • First day of light in a beta of Netscape 2 in December 1995 • IE followed suit with JScript in 1996
  • 10. Has NOTHING to do with Java!
  • 11. • JavaScript is one of the world’s most popular programming languages • One interpreter on every machine • ECMAScript standardizing - Fifth edition • Web browsers becoming much faster
  • 20. Function declaration: function benQuote () { ! return "Rumors about me? Calista Flockhart, Pam Anderson, and Matt Damon. That's who I'm dating."; }
  • 22. • If • Switch • Shorthand assignment • Ternary operators
  • 23. function makeMovie (withLivTyler) { ! var nice = withLivTyler || false; }
  • 26. • = Assignment • == Equality • === Identity
  • 27. // Assignment var bestFriend = "Matt Damon"; // Equality if (5 == "5") { ! // true } // Identity if (5 === "5") { ! // false }
  • 28. // Short-circuit logic if (true || false) if (false && true) // Makes this code safe if (obj && obj.property)
  • 29. // Short-circuit logic if (true || false) if (false && true) // Makes this code safe if (obj && obj.property)
  • 31. // true 5 == "5" // 123 "1" + 2 + 3;
  • 32. // 6, manual type conversion parseInt("1", 10) + 2 + 3;
  • 33. null == undefined == 0 == false == "" • Not really, but sort of • Rather “truthy” or “falsy”
  • 34. var a = null; var b; // undefined var c = 0; var d = false; var e = ""; if (a) // false if (b) // false if (c) // false if (d) // false if (e) // false
  • 36. • string • number • boolean • null • undefined • Object
  • 37. Types of Object include: • function • Array • Date • RegExp
  • 39. typeof return values: • string • number • boolean • function • object • undefined
  • 40. typeof fanClub // "undefined" var title = "Armageddon"; typeof title // Equals "string" var age = 37; typeof age // Equals "number"
  • 41. function anotherQuote () { ! return "If I ever woke up with a dead hooker in my hotel room, Matt would be the first person I'd call."; } typeof anotherQuote; //"function"
  • 42. var obj = {}; typeof obj = // "object" var arr = ["B", "E", "N"]; typeof arr // "object"
  • 43. var obj = {}; typeof obj = // "object" var arr = ["B", "E", "N"]; typeof arr // "object" ?!
  • 45. obj instanceof Array // false arr instanceof Array // true
  • 47. Procedural function notAHit () { ! return "Gigli"; }
  • 48. Functions as variables var wroteScript = function () { ! return "Good Will Hunting"; }; wroteScript();
  • 49. Anonymous document.onmousemove = function (evt) { alert(evt.pageX); };
  • 50. Self-invoking (function () { ! var dogma = "Shot in 1999"; })();
  • 51. Self-invoking (function () { ! var dogma = "Shot in 1999"; })();
  • 53. • Any argument can be omitted • Any argument can be added • No overloading • The arguments collection
  • 54. function concat (a, b, c) { ! return a + b + c; } concat(1, 2, 3); // 6 concat(1, 2); // NaN
  • 55. • The arguments collection • Property: arguments.length • NOT an array
  • 56. function concat () { ! var sum = 0, l = arguments.length; ! for (var i=0; i<l; i++) { ! ! sum += arguments[i]; ! } ! return sum; } concat(1, 2, 3); // 6 concat(1, 2); // 3 concat(1, 2, 7, 11, 5); // 26
  • 58. function Ben () { ! this.name = "Ben Affleck"; ! this.gotAnOscar = true; }; var ben = new Ben(); alert(ben.gotAnOscar); // true Object constructor
  • 59. var ben = { ! name : "Ben Affleck", ! gotAnOscar : true }; alert(ben.name); // "Ben Affleck" Object literal
  • 60. Different syntax, same thing: ben["arms"] = 2; ben.arms = 2;
  • 61. Different syntax, same thing: ben["arms"] = 2; ben.arms = 2;
  • 62. For any object: var ben = {}; ben[1972] = "Year of birth"; ben["born"] = 1972; ben[true] = false;
  • 63. var regEx = new RegExp; regEx[3] = "I can do this?";
  • 64. var goodMovie = { ! title : "Good Will Hunting", ! year : 1997 }; for (var item in goodMovie) { ! alert(item + ": " + goodMovie[item]); }
  • 65. var goodMovie = { ! title : "Good Will Hunting", ! year : 1997 }; // Check returns true if ("year" in goodMovie) { ! alert(goodMovie.year); }
  • 68. • The prototype chain checks itself first • It then goes to the parent, parent’s parent etc...
  • 69. function Being () { ! this.living = true; } Being.prototype.greet = function () { ! return "Hello!"; };
  • 70. function Ben () { ! this.talks = true; } Ben.prototype = new Being; Ben.prototype.saySomething = function () { ! return "I feel like fame is wasted on me."; };
  • 71. // Create an instance var ben = new Ben(); // Returns "I feel like fame is wasted on me." ben.saySomething(); // Returns "Hello!", inherited // from the Being object ben.greet();
  • 72. Checking for the greet() method in this order: • ben instance • Ben prototype • Being prototype • Object prototype
  • 73. • Simple JavaScript Inheritance • A Base Class for JavaScript Inheritance • Defining classes and inheritance Class-based mimicking
  • 74. • It’s native, i.e. no dependencies • Freedom of style and version • Easy readability • Code handover Why prototype syntax
  • 75. “I have been writing JavaScript for 8 years now, and I have never once found need to use an uber function... ...I now see my early attempts to support the classical model in JavaScript as a mistake.” - Douglas Crockford Why prototype syntax
  • 76. Scope
  • 77. • Scope refers to where variables and functions are accessible • In what context something is being executed
  • 78. • Basically, global or local • Variables have function scope • Functions have the same scope as variables
  • 79. // Global var likesToPlay = "Poker"; function getGame () { ! // Local ! var likesToPlay = "Hold ‘em"; ! // Global ! playOnline = true; ! return likesToPlay; ! // Returns "Hold ‘em" }
  • 80. function playPoker (money) { ! if (money) { ! ! var willPlay = true; ! } ! // Perfectly valid ! return willPlay; }
  • 81. function global () { ! return "Access anywhere"; }
  • 82. function outer () { ! function inner () { ! ! return "Inner"; ! } ! return inner(); } outer(); // Accessible inner(); // Not accessible
  • 83. “Global scope is like a public toilet. You can’t avoid going in there. But try to limit your contact with surfaces when you do.” - Dmitry Baranovskiy, Raphaël JS library Polluting the global namespace
  • 85. • Run a function in a certain context • The call and apply methods • Defined for all functions
  • 86. function docReady () { ! alert(this); ! // this is the window object } window.onload = docReady;
  • 87. function setName (name) { ! this.name = name; ! // document.name === "Bennifer" } document.onclick = function () { ! setName.call(document, "Bennifer"); };
  • 88. function setName (name) { ! this.name = name; ! // document.name === "Bennifer" } document.onclick = function () { ! setName.call(document, "Bennifer"); };
  • 89. function setNames () { ! this.firstName = arguments[0]; ! this.lastName = arguments[1]; // document.firstName === “Ben” // document.lastName === “Affleck” } function callSetNames () { ! setNames.apply(document, arguments); }; callSetNames("Ben", "Affleck");
  • 90. function setNames () { ! this.firstName = arguments[0]; ! this.lastName = arguments[1]; // document.firstName === “Ben” // document.lastName === “Affleck” } function callSetNames () { ! setNames.apply(document, arguments); }; callSetNames("Ben", "Affleck");
  • 96. • Closures are expressions, usually functions, which can work with variables set within a certain context • Inner functions referring to local variables of its outer function create closures
  • 97. function add (x) { ! return function (y) { ! ! return x + y; ! }; } var add5 = add(5); var no7 = add5(2); // Equals 7
  • 99. function add (x) { ! return function (y) { ! ! return x + y; ! }; } var add5 = add(5); // How JavaScript sees it var add5 = function (y) { ! return 5 + y; }
  • 100. function add (x) { ! return function (y) { ! ! return x + y; ! }; } var add5 = add(5); // How JavaScript sees it var add5 = function (y) { ! return 5 + y; }
  • 101. function addLinks () { ! for (var i=0, link; i<5; i++) { ! ! link = document.createElement("a"); ! ! link.innerHTML = "Link " + i; ! ! link.onclick = function () { ! ! ! alert(i); ! ! }; ! ! document.body.appendChild(link); ! } } window.onload = addLinks;
  • 102. function addLinks () { ! for (var i=0, link; i<5; i++) { ! ! link = document.createElement("a"); ! ! link.innerHTML = "Link " + i; ! ! link.onclick = function () { ! ! ! alert(i); ! ! }; ! ! document.body.appendChild(link); ! } } window.onload = addLinks; ! ! link.onclick = function () { ! ! ! alert(i); ! ! };
  • 103. function addLinks () { ! for (var i=0, link; i<5; i++) { ! ! link = document.createElement("a"); ! ! link.innerHTML = "Link " + i; ! ! link.onclick = function (num) { ! ! ! return function () { ! ! ! ! alert(num); ! ! ! }; ! ! }(i); ! ! document.body.appendChild(link); ! } } window.onload = addLinks;
  • 104. function addLinks () { ! for (var i=0, link; i<5; i++) { ! ! link = document.createElement("a"); ! ! link.innerHTML = "Link " + i; ! ! link.onclick = function (num) { ! ! ! return function () { ! ! ! ! alert(num); ! ! ! }; ! ! }(i); ! ! document.body.appendChild(link); ! } } window.onload = addLinks; ! ! link.onclick = function (num) { ! ! ! return function () { ! ! ! ! alert(num); ! ! ! }; ! ! }(i);
  • 105. function addLinks () { ! for (var i=0, link; i<5; i++) { ! ! link = document.createElement("a"); ! ! link.innerHTML = "Link " + i; ! ! link.onclick = function (num) { ! ! ! return function () { ! ! ! ! alert(num); ! ! ! }; ! ! }(i); ! ! document.body.appendChild(link); ! } } window.onload = addLinks; ! ! link.onclick = function (num) { ! ! ! return function () { ! ! ! ! alert(num); ! ! ! }; ! ! }(i);
  • 106. function addLinks () { ! for (var i=0, link; i<5; i++) { ! ! link = document.createElement("a"); ! ! link.innerHTML = "Link " + i; ! ! link.onclick = function (num) { ! ! ! return function () { ! ! ! ! alert(num); ! ! ! }; ! ! }(i); ! ! document.body.appendChild(link); ! } } window.onload = addLinks; ! ! link.onclick = function (num) { ! ! ! return function () { ! ! ! ! alert(num); ! ! ! }; ! ! }(i);
  • 107. function addLinks () { ! for (var i=0, link; i<5; i++) { ! ! link = document.createElement("a"); ! ! link.innerHTML = "Link " + i; ! ! link.onclick = function (num) { ! ! ! return function () { ! ! ! ! alert(num); ! ! ! }; ! ! }(i); ! ! document.body.appendChild(link); ! } } window.onload = addLinks; ! ! link.onclick = function (num) { ! ! ! return function () { ! ! ! ! alert(num); ! ! ! }; ! ! }(i);
  • 109. • Origins from Douglas Crockford • Singleton pattern • Offers private and public members
  • 110. var goneBabyGone = function () { ! // Private members ! var movieTitle = "Gone Baby Gone", isDirectedByBen = true; ! ! // Public members ! return { ! ! title : function () { ! ! ! return movieTitle; ! ! }, ! ! ! ! directedByBen : function () { ! ! ! return isDirectedByBen; ! ! } ! }; }();
  • 111. var goneBabyGone = function () { ! // Private members ! var movieTitle = "Gone Baby Gone", isDirectedByBen = true; ! ! // Public members ! return { ! ! title : function () { ! ! ! return movieTitle; ! ! }, ! ! ! ! directedByBen : function () { ! ! ! return isDirectedByBen; ! ! } ! }; }();
  • 112. var goneBabyGone = function () { ! // Private members ! var movieTitle = "Gone Baby Gone", isDirectedByBen = true; ! ! // Public members ! return { ! ! title : function () { ! ! ! return movieTitle; ! ! }, ! ! ! ! directedByBen : function () { ! ! ! return isDirectedByBen; ! ! } ! }; }();
  • 113. var goneBabyGone = function () { ! // Private members ! var movieTitle = "Gone Baby Gone", isDirectedByBen = true, ! ! title = function () { ! ! ! return movieTitle; ! ! }, ! ! ! ! directedByBen = function () { ! ! ! return isDirectedByBen; ! ! }; ! ! // Public members ! return { title : title, directedByBen : directedByBen ! }; }();
  • 115. • Avoiding global variables • Code structure • Extending, but not necessarily inheriting
  • 116. // Create a Ben object var Ben = {}; // Set functionality Ben.Director = function () { ! var noOfMovies = 4; ! return { ! ! movies : function () { ! ! ! return noOfMovies; ! ! } ! }; }();
  • 117. // Assertion if (typeof Ben === "undefined") { ! Ben = {}; } Ben.Actor = function () { ! var noOfMovies = 51; ! return { ! ! actAndDirectorCount : function () { ! ! ! return noOfMovies + " as actor & " + Ben.Director.movies.call(this) + " as Director"; ! ! } ! }; }();
  • 118. Sugar & spice It’s awfully nice!
  • 120. // A little sugar String.prototype.trim = function () { ! return this.replace(/^s*|s*$/g, ""); }; var monkey = " Monkey "; monkey.trim(); //"Monkey"
  • 121. // Currying function add () { ! var sum = 0; ! for (var i=0, il=arguments.length; i<il; i++) { ! ! sum += arguments[i]; ! }; ! return sum; }
  • 122. // Currying (continued) - Currying method by Crockford! ! Function.prototype.curry = function () { ! var slice = Array.prototype.slice, ! ! args = slice.apply(arguments), ! ! that = this; ! return function () { ! ! ! return that.apply( ! ! ! ! null, args.concat(slice.apply(arguments)) ! ! ! ); ! }; } var add8 = add.curry(5, 3); alert(add8(1, 3, 7)); // 19
  • 123. // Currying (continued) - Currying method by Crockford! ! Function.prototype.curry = function () { ! var slice = Array.prototype.slice, ! ! args = slice.apply(arguments), ! ! that = this; ! return function () { ! ! ! return that.apply( ! ! ! ! null, args.concat(slice.apply(arguments)) ! ! ! ); ! }; } var add8 = add.curry(5, 3); alert(add8(1, 3, 7)); // 19
  • 124. // Currying (continued) - Currying method by Crockford! ! Function.prototype.curry = function () { ! var slice = Array.prototype.slice, ! ! args = slice.apply(arguments), ! ! that = this; ! return function () { ! ! ! return that.apply( ! ! ! ! null, args.concat(slice.apply(arguments)) ! ! ! ); ! }; } var add8 = add.curry(5, 3); alert(add8(1, 3, 7)); // 19
  • 125. // Currying (continued) - Currying method by Crockford! ! Function.prototype.curry = function () { ! var slice = Array.prototype.slice, ! ! args = slice.apply(arguments), ! ! that = this; ! return function () { ! ! ! return that.apply( ! ! ! ! null, args.concat(slice.apply(arguments)) ! ! ! ); ! }; } var add8 = add.curry(5, 3); alert(add8(1, 3, 7)); // 19
  • 126. // Currying (continued) - Currying method by Crockford! ! Function.prototype.curry = function () { ! var slice = Array.prototype.slice, ! ! args = slice.apply(arguments), ! ! that = this; ! return function () { ! ! ! return that.apply( ! ! ! ! null, args.concat(slice.apply(arguments)) ! ! ! ); ! }; } var add8 = add.curry(5, 3); alert(add8(1, 3, 7)); // 19
  • 127. // Currying (continued) - Currying method by Crockford! ! Function.prototype.curry = function () { ! var slice = Array.prototype.slice, ! ! args = slice.apply(arguments), ! ! that = this; ! return function () { ! ! ! return that.apply( ! ! ! ! null, args.concat(slice.apply(arguments)) ! ! ! ); ! }; } var add8 = add.curry(5, 3); alert(add8(1, 3, 7)); // 19
  • 129. • No real standard, only best practices • Recommended tool: JSLint
  • 131. • Embrace JavaScript • Don’t try to make it into Java, C or any other language • Learn to love it and its dynamic, loose and prototypical nature
  • 132. This is how we roll
  • 133. Robert Nyman robertnyman.com/speaking/ robert@robertnyman.com Twitter: @robertnyman Pictures: Brendan - http://www.flickr.com/photos/mollyeh11/279367481/ Yoda - http://buzzybeegirl.files.wordpress.com/2008/12/yoda-400x3001.jpg Twitter - http://twitter.com/manssandstrom/status/1528315581 Gmail - http://www.flickr.com/photos/webber/71748774/ Slow - http://www.feministing.com/archives/012345.html Crockford - http://www.flickr.com/photos/charliebrewer/2897862701/ Obi-Wan - http://enterthecircle.files.wordpress.com/2009/01/obi-wan-kenobi-01-large.jpg Ben Affleck - http://www.flickr.com/photos/sasy/3993866442/ Squat toilet - http://www.flickr.com/photos/35034350906@N01/4080372999 Cuddling bears - http://www.nogg.se/blogg.asp?intShowMenu=a2&idHomepage=6951&idBloggCategory=6162 Winnie The Pooh and friends - http://mammacarola.blogg.se/2009/april/ IEVoodoo Doll - http://nexus404.com/Blog/2007/10/26/make-your-own-internet-explorer-voodoo-doll-a-step-by-step-guide/ Ben Affleck confused - http://cdn.buzznet.com/assets/imgx/4/9/0/5/8/orig-49058.jpg