The document discusses several key aspects of JavaScript functions including: 1. Functions can be defined in 3 ways - with the function keyword, a function expression, or a function declaration. 2. Closures allow functions to access variables from outer scopes even after the outer function has closed. This allows functions to cache values. 3. Functions are objects that can be passed around and assigned to variables like any other object. 4. Prototypal inheritance is used in JavaScript to inherit properties and methods from one object to another using prototypes. 5. The this keyword is dynamically bound based on the invocation context of a function. Understanding how this works is important for using objects correctly.

1. Intro to jQuery
Web Development 101
Lesson 03.01

2. jQuery is great

4. Advanced Javascript.
Web Development 101
Lesson 03.01

5. OR
What 80% of Javascript programmers don’t know
about their own language.

6. // The .bind method from Prototype.js
Function.prototype.bind = function() {
var fn = this,
args = Array.prototype.slice.call(arguments),
object = args.shift();
return function() {
return fn.apply(
object,
args.concat(
Array.prototype.slice.call(arguments)
)
);
};
};

7. What ways can we define functions?

8. function funcA(){ return true; }
var funcB = function(){ return true; };
window.funcC = function(){ return true; };
!
assert( funcA() && funcB() && funcC() );

9. var funcB = function(){ return true; };
window.funcC = function(){ return true; };
!
assert( funcA() && funcB() && funcC() );
!
function funcA(){ return true; }

10. function stealthCheck(){
assert( stealth() );
!
return stealth();
!
function stealth(){ return true; }
}
!
stealthCheck();

11. function factorial(n) {
return n * (n > 1 ? factorial(n - 1) : 1);
}
!
factorial(10);

12. var factorial = function f(n) {
return n * (n > 1 ? f(n - 1) : 1);
}
!
factorial(10); // Works
f(10);
// Undefined function

13. Is a function an object?

14. var obj = {};
var fn = function(){};
!
obj.prop = "some value";
fn.prop = "some value";

15. var factorial = function f(n) {
f.cache = f.cache || {};
if (!f.cache[n]) {
f.cache[n] = n * (n > 1 ? f(n - 1) : 1);
}
return f.cache[n];
}
!
factorial(10);
factorial(9);
factorial(20);

16. How does `this` work?

17. var katana = {
isSharp: true,
use: function(){
this.isSharp = false;
}
};
!
katana.use();
katana.isSharp === false;

18. function katana(){
this.isSharp = true;
}
katana();
isSharp === true;
!
!
var shuriken = {
toss: function(){
this.isSharp = true;
}
};
shuriken.toss();
shuriken.isSharp === true;

19. How do I change `this`?

20. var object = {};
function fn(){
return this;
}
!
fn() === this === window;
!
fn.call(object) === object;

21. var object = {a: ‘Jeremiah’, b: ‘Baruch’};
!
function getAttr(a){
return this[a];
}
!
getAttr.call(object, ‘a’) === ‘Jeremiah’;
!
getAttr.apply(object, [‘b’]) === ‘Baruch’;

22. Can I instantiate a function?

23. function Pioneer(){
this.name = "Pioneer";
}
!
joe = Pioneer();
joe === undefined;
!
joe = new Pioneer();
joe.name == "Pioneer";

24. function Pioneer(){
this.hasBibleStudy = false;
!
this.preach = function() {
this.hasBibleStudy = true;
};
}
!
jack = new Pioneer();
jill = new Pioneer();
!
jack.hasBibleStudy === false;
jill.hasBibleStudy === false;
!
jack.preach();
!
jack.hasBibleStudy === true;
jill.hasBibleStudy === false;

25. function Pioneer(){
this.hasBibleStudy = false;
!
this.preach = function() {
this.hasBibleStudy = true;
};
}
!
jack = Pioneer();
jill = Pioneer();
!
jack.hasBibleStudy === false; // Fatal Type Error
jill.hasBibleStudy === false;
!
jack.preach();
!
jack.hasBibleStudy === true;
jill.hasBibleStudy === false;

26. Can I build a function with variable
number of arguments?

27. var object = {a: ‘Jeremiah’, b: ‘Baruch’};
!
function getAttr(a){
return this[a];
}
!
getAttr.apply(object, [‘b’]) === ‘Baruch’;

28. var object = {a: ‘Jeremiah’, b: ‘Baruch’};
!
function getAttr() {
var out = [], i;
for (i = 0; i < arguments.length; i++) {
out.push( this[ arguments[i] ] );
}
return out;
}
!
getAttr.apply(object, [‘a’, ‘b’]) ===
[‘Jeremiah’, ‘Baruch’];

29. function smallest(array){
return Math.min.apply( Math, array );
}
!
function largest(array){
return Math.max.apply( Math, array );
}
!
assert(smallest([0, 1, 2, 3]) == 0);
assert(largest([0, 1, 2, 3]) == 3);

30. function smallest() {
return Math.min.apply( Math, arguments );
}
!
function largest() {
return Math.max.apply( Math, arguments );
}
!
assert(smallest(0, 1, 2, 3) == 0);
assert(largest(0, 1, 2, 3) == 3);

31. function highest(){
return arguments.sort(function(a, b) {
return b - a;
});
}
!
highest(1, 1, 2, 3)[0] === 3;

32. function highest(){
return arguments.sort(function(a, b) {
return b - a;
});
}
!
highest(1, 1, 2, 3)[0] === 3; // Fatal Error.

33. `arguments` isn’t actually an array

34. function highest() {
var argArray = Array().slice.call(arguments);
return argArray.sort(function(a, b) {
return b - a;
});
}
!
highest(1, 1, 2, 3)[0] === 3;

35. How do Closures work?

36. var a = 5;
!
function runMe(a) {
assert( a == ___, "Check the value of a." );
!
function innerRun(){
assert( b == ___, "Check the value of b." );
assert( c == ___, "Check the value of c." );
}
!
var b = 7;
innerRun();
var c = 8;
}
!
runMe(6);
!
for ( var d = 0; d < 3; d++ ) {
setTimeout(function(){
assert( d == ___, "Check the value of d." );
}, 100);
}

37. var a = 5;
!
function runMe(a) {
assert( a == 6, "Check the value of a." );
!
function innerRun(){
assert( b == 7, "Check the value of b." );
assert( c == undefined, "Check the value of c." );
}
!
var b = 7;
innerRun();
var c = 8;
}
!
runMe(6);
!
for ( var d = 0; d < 3; d++ ) {
setTimeout(function(){
assert( d == 3, "Check the value of d." );
}, 100);
}

38. !
for ( var d = 0; d < 3; d++ ) {
setTimeout(function(){
assert( d == 3, "Check the value of d." );
}, 100);
}

39. for (var d = 0; d < 3; d++) {
(function (d) {
setTimeout(function () {
console.log(d);
}, 100);
}(d));
}

40. Code smell: Don’t make closures
inside a loop. Normally.

41. How do I make a class?

42. #!/usr/bin/env python
!
class Pioneer(object):
def __init__(self, name):
self.name = name
self.bibleStudies = 0
!
def preach(self):
self.bibleStudies += 1
!
joe = Pioneer(“Joe”)
joe.preach();

43. #!/usr/bin/env php
!
class Pioneer {
private name;
private bibleStudies;
!
public function __construct(name) {
this.name = name;
this.bibleStudies = 0;
}
!
public function preach() {
this.bibleStudies++;
}
}
!
joe = new Pioneer(“Joe”);
joe->preach();

44. Write `Pioneer` in JS.

45. var Pioneer = function(name) {
this.name = name;
this.bibleStudies = 0;
!
this.preach = function() {
this.bibleStudies++;
};
};
!
joe = new Pioneer(“Joe”);
joe.preach();

46. var Pioneer = function(name) {
this.name = name;
this.bibleStudies = 0;
};
!
Pioneer.prototype = {};
Pioneer.prototype.preach = function() {
this.bibleStudies++;
};
!
joe = new Pioneer(“Joe”);
joe.preach();

47. Inheritance. Prototypal Inheritance.

48. var Pioneer = function (name) {
this.name = name;
this.bibleStudies = 0;
};
!
Pioneer.prototype = {};
Pioneer.prototype.preach = function () {
this.bibleStudies++;
};
!
var SpecialPioneer = function(name) {
this.name = name;
this.bibleStudies = 0;
};
!
SpecialPioneer.prototype = new Pioneer();
SpecialPioneer.prototype.preach = function () {
this.bibleStudies += 5;
};
!
var joe = new Pioneer("Joe"),
jeremy = new SpecialPioneer('Jeremy');
!
joe.preach();
jeremy.preach();

49. Enforcing Function Context

50. var Button = {
click: function(){
this.clicked = true;
}
};
!
var elem = document.createElement("li");
elem.innerHTML = "Click me!";
elem.onclick = Button.click;
document.getElementById("results").appendChild(elem);
!
elem.onclick();
!
Button.clicked === undefined;
elem.clicked === true;

51. function bind(context, name){
return function() {
return context[name].apply(context, arguments);
};
}
!
var Button = {
click: function(){
this.clicked = true;
}
};
!
var elem = document.createElement("li");
elem.innerHTML = "Click me!";
elem.onclick = bind(Button, "click");
document.getElementById("results").appendChild(elem);
!
elem.onclick();
!
Button.clicked === true;
elem.clicked === undefined;

52. Function.prototype.bind = function(object) {
var fn = this;
return function(){
return fn.apply(object, arguments);
};
};
!
var Button = {
click: function(){
this.clicked = true;
}
};
!
var elem = document.createElement("li");
elem.innerHTML = "Click me!";
elem.onclick = Button.click.bind(Button);
document.getElementById("results").appendChild(elem);
!
elem.onclick();
!
Button.clicked === true;

53. Back to our original goal

54. // The .bind method from Prototype.js
Function.prototype.bind = function() {
var fn = this,
args = Array.prototype.slice.call(arguments),
object = args.shift();
return function() {
return fn.apply(
object,
args.concat(
Array.prototype.slice.call(arguments)
)
);
};
};

55. Function.prototype.bind = function(){
var fn = this, args = Array.prototype.slice.call(arguments), object = args.shift();
return function(){
return fn.apply(object,
args.concat(Array.prototype.slice.call(arguments)));
};
};
!
var Button = {
click: function(value) {
this.clicked = value;
}
};
!
var elem = document.createElement("li");
elem.innerHTML = "Click me!";
elem.onclick = Button.click.bind(Button, “I was clicked!”);
document.getElementById("results").appendChild(elem);
!
elem.onclick();
!
Button.clicked === “I was clicked!”

57. Functions can be defined 3
ways
Closures can be used to cache
values for later, including
execution scope.
Functions are just objects that
you can execute.
Objects inherit from each other
using prototypes.
The `this` keyword is bound to
function context
Build in object prototypes can
be extended.
No classes, just objects.
All of that works without
including jQuery at all.

58. Moral of the story

59. Javascript is a great, although quirky, language.
Prototypal inheritance works similarly, but not exactly like class
inheritance.
jQuery is a great library. You should use it for DOM and AJAX code.
Reading API documentation will teach you jQuery. A good
understanding of Javascript is harder to come by.

60. :rewind

61. var Pioneer = function (name) {
this.name = name;
this.bibleStudies = 0;
};
!
Pioneer.prototype = {};
Pioneer.prototype.preach = function () {
this.bibleStudies++;
};
!
var SpecialPioneer = function(name) {
this.name = name;
this.bibleStudies = 0;
};
!
SpecialPioneer.prototype = new Pioneer();
SpecialPioneer.prototype.preach = function () {
this.bibleStudies += 5;
};
!
var joe = new Pioneer("Joe"),
jeremy = new SpecialPioneer('Jeremy');
!
joe.preach();
jeremy.preach();

62. Let’s make inheritance better.

63. var Person = Class.extend({
init: function (isDancing) {
this.dancing = isDancing;
},
dance: function () {
return this.dancing;
}
});
!
var Ninja = Person.extend({
init: function () {
this._super(false);
},
dance: function () {
// Call the inherited version of dance()
return this._super();
},
swingSword: function () {
return true;
}
});
!
var p = new Person(true);
p.dance(); // => true
!
var n = new Ninja();
n.dance(); // => false
n.swingSword(); // => true
!
// Should all be true
p instanceof Person && p instanceof Class && n instanceof Ninja && n instanceof Person && n instanceof Class