Bottom Up

Bottom Up JavaScript


Provide a JavaScript development foundation.

The only 3 things you ever do with JavaScript:
0. Load Scripts
1. Attach Event Listener
2. Get or modify Data
3. Update the page

Extra burdens:
Unusual Language Features
Multiple Environments and Languages
Divergent and Competing Libraries
Unusual Performance Considerations
Scattered Resources and Development Tools

©Jupiter IT JavaScriptMVC


What We Will Learn

We will learn 'OF' just about everything:

The JavaScript (JS) Language
The Document Object Model (DOM)
How JS and the DOM cooperate
Libraries
Development Tools
Resources



JavaScript

JavaScript is a dynamic, weakly typed, prototype-
based language with first-class functions.

JavaScript != Java
JavaScript == A real programming language
JavaScript == ECMAScript == Jscript
JavaScript != Document Object Model

JavaScript is typically used in browsers to power
dynamic websites.

JS code is loaded and ran with script tags:
<script type='text/javascript'>alert('hi')</script>
<script type='text/javascript' src='myjs.js'></script>



JavaScript: Dynamic

Compilation and execution happen together.

a = function(){ return 'a' };
b = function(){ return 'b' };
if(Math.random() < 0.5)
c = a;
else
c = b;
a() -> 'a'
b() -> 'b'
c() -> ???

Use these techniques to remove boilerplate
code.



JavaScript: Weakly Typed

Type associated with value, not variable.

var a = 1;
a = “one”;
a = [1];
a = {one: 1};

Use typeof, instanceof, or other duck typing
techniques to determine type.

typeof “abc” -> “string”
typeof 1 -> “number”
typeof [] -> “object”



JavaScript: Prototype-based

Prototype looks up inherited and shared properties.
Animal = function(name) { this.name = name }
Animal.prototype.toString = function(){
return this.name+" has multiple cells, diploid blastula."
}
Chordate = function(name){ this.name = name; }
Chordate.prototype = new Animal();
Chordate.prototype.has_spine = true;
Mammal = function(name){ this.name = name; }
Mammal.prototype = new Chordate();
Mammal.prototype.has_hair = true;

has_hair has_spine
Chrdate
Mmml Chrdate
Animal Animal
toString
Object
p proto Object
p proto p
prototype prototype prototype

Mmml Chrdate Animal



JavaScript: First Class Functions

Functions are just like objects, except you
can put a () after them.
//create
square1 = new Function(“x”,”return x*x”);
square2 = function(x){ return x*x};

mult = function(f1, f2){
return function(n){ //return
return f1(n) * f2(n)
}
}
bigF = mult(square1, square2) //pass
bigF(2) -> 16;



JavaScript: Data Types

Basic data types:
● Undefined -> undefined
● Null -> null
● Boolean -> true, false
● String -> “hello”
● Number -> 2, 0.2
● Object -> {name: “value”}
● Function -> function(){}
● Array -> [1,2,3]
● Date -> new Date()
● RegExp -> /.*/g, new RegExp(“.*”,”g”)



Document Object Model

JS Representation of HTML and browser.
<html>
<head></head>
<body>
<h1>hi</h1>
</body>
</html>

document = {
documentElement: {
nodeName: “HTML”
childNodes: [
{nodeName: “HEAD”, childNodes: []},
{
nodeName : “BODY”
childNodes: [{nodeName: 'h1', innerHTML: "hi"}]
}
]
},
getElementById : function(id){ ... }
}



Document Object Model

JS Representation of HTML and browser.
Browser
navigator.userAgent
Page
location
Document
var el=document.getElementById('eid')
Ajax
new XMLHttpRequest()
Events
el.attachEventListener('click',f,false)
Elements
el.style.backgroundColor = “blue” Source: Wikipedia



Three Things

1. Respond to an event
Find Element -> Document / Element
Attach Event Listener -> Element
...
2. Get or Modify Data
...
From Server -> XMLHttpRequest / Ajax
From HTML -> Document / Element
From Location -> Location
...
3. Update the Page
...
Change Element -> Element
Change Location -> Location



Three Things
Use the DOM for each part, stitch it together with JS.

<a id='find_price'>Find Price</a>
<div id='price'></div>

var el = FindElement('find_price')
el.AttachFunctionToRunOn('click',getAndSetPrice)

function getAndSetPrice(){
price = GetDataFrom('/getPrice')
...
3. Update the Page
...
var pel = FindElement('price')
pel.InsertText(price)
}



Three Things
<a id='find_price'>Find Price</a>
<div id='price'></div>

var el=document.getElementById('find_price') //FindElement
el.attachEventListener('click', getAndSetPrice, false); //attach

getAndSetPrice = function(event){
var xhr = new XMLHttpRequest() //GetDataFrom
xhr.open("GET", "/getPrice", false); //don't do this!
xhr.send();
var price = xhr.responseText;
...
3. Update the Page
...
document.getElementById('price').innerHTML = price;
}



Libraries

Exist to make things easier:
Browser inconsistencies
attachEvent vs addEventListener
XMLHttpRequest vs ActiveXObject

DOM API weaknesses
$('#sidebar .ul').height()
document.getElementById('sidebar').
childNodes[2].offsetHeight

Common tasks
Drag/drop, AutoComplete, Slider, Sortable Tables

Language improvements
[].each(), “isRed”.startsWith(“is”)

Do you need a library -> YES!!!


Library Selection



Tools

Debugging
Firebug (FF)
MS Visual Web Developer (IE)
DragonFly (Opera)
Chrome
Drosera / Web Inspector (Safari)

Compression
Dojo Shrink Safe
YUI
Dean Edwards Packer / Compress.js

Performance
Yslow
Firebug
Chrome's development tools



Tools Continued ...

Testing
In browser (easy) - JSUnit
Browser Control (comprehensive) - Selenium
Simulated (fast) – Env.js

Documentation
JSDoc – Understands JavaScript, hard to document complex
features
Natural Docs – Can document anything
MVCDoc – Can document anything, understands some JS.



Resources

Documentation
Mozilla Development Center
MSDN Internet Explorer Development Center
Quirksmode

Books
JavaScript - the Definitive Guide. David Flanagan
JavaScript – the Good Parts. Douglas Crockford

News
Ajaxian
Ejohn.org



Three Things Revisited

0. Load Script

<script type='text/javascript' src='production.js'></script>

1. Respond to an event
//Attach event handlers when you know the document is ready
$(function(){
$(“#find_price”).click(function(event){
...
...
$.get('/getPrice',function(price){
...
3. Update the Page
...
$(“#price”).text(price);
});
})



Three Things Revisited Cont...
MyCo.updatePrice = function(price){
$(“#price”).text(price);
}
MyCo.getAndUpdatePrice = function(){
$.get('/getPrice',MyCo.updatePrice)
}
$(function(){
$(“#find_price”).click(MyCo.getAndUpdatePrice)
})
OR Maybe ...
$.Controller.extend('MyCo.Controllers.FindPrice',{
click : function(){
MyCo.Price.get(this.callback('updatePrice'))
},
updatePrice : function(price){
$(“#price).html({view: 'price',data: {price: price});
}
})

Your price is <span class='highlight'><%= price %></span>



What we've learned

The JavaScript (JS) Language
The Document Object Model (DOM)
How JS and the DOM cooperate
Libraries
Development Tools
Resources


Bottom Up

Related slideshows

Recommended for you

Recommended for you

Recommended for you

Recommended for you

Recommended for you

More Related Content

What's hot

What's hot (20)

Similar to Bottom Up

Similar to Bottom Up (20)

More from Brian Moschel

More from Brian Moschel (11)

Recently uploaded

Recently uploaded (20)

Bottom Up