JavaScript Needn't Hurt!

JavaScript Needn’t Hurt! Thomas Kjeldahl Nilsson [email_address] linkedin.com/in/thomaskjeldahlnilsson twitter.com/thomanil

Who Are You? Done any JavaScript? Dozen lines of code? Hundreds? Thousands?

Who Am I? JavaScript enthusiast Hundreds of hours Thousands lines of code Not an expert!

What Are We Covering Today? Language basics Html scripting Good practices Tools

What Rocks? Powerful, elegant, dynamic Present & enabled for most users Not confined to the browser Small learning surface

What Sucks? Rushed out the door Some bad language features Crossbrowser problems

Development Environment Walkthrough

Language Basics Syntax Types Variables Objects Functions

Basic Syntax Similar to Java, C# Operators, statements if-else, while, for, try-catch-finally Still in Kansas...

Types Strings Numbers Booleans Objects Arrays

Variable Declarations var x = “foo”; // string var x = 2; // number var x = true; // boolean var x = { }; // object var x = [ ]; // array

Object Creation Literal Form var BasicProject = { name : "Steria Workshop", version : 1.2, getName : function() { return this.name; } };

Object Creation Dynamic Form var BasicProject = {}; BasicProject.name = "Steria Workshop"; BasicProject.version = 1.2; BasicProject.getName = function() { return this.name; };

Objects as Maps (Associative Arrays) var Person = { firstname:"John", lastname:"Smith" }; Person.firstname; // => "John" (Access using identifier) Person["firstname"]; // => "John" (Access using variable name)

Arrays are Special Case of Object var arr = []; // Always declared without size. // Grows as needed. arr[0] = true; arr[3] = "john"; arr[300] = { description : "object!" }; arr[100]; // => Undefined arr.length; // => 301

Arrays and Objects Can Be Deeply Nested var OuterObject = { innerArray : [ innerObject : { deepestArray : [1,2,3] } ] };

JSON {"firstName":"Gustav","lastName":"Adolf", "roles":["King of Sweden","Terrible shipbuilder"], "other":{"birth":"9.12.1594","death":"16.11.1632"}}

Kind Familiar Looking { "firstName" : "Gustav", "lastName" : "Adolf", "roles" : [ "King of Sweden", "Terrible shipbuilder" ], "other" : { "birth" : "9.12.1594", "death" : "16.11.1632" } }

JavaScript Object Literal! var EvaluatedObject = { firstName : "Gustav", lastName : "Adolf", roles : [ "King of Sweden", "Terrible shipbuilder" ], other : { birth : "9.12.1594", death : "16.11.1632" } } ;

Prototypal Inheritance (Simplified) var Employee = {name : "CEO Jack", company : "ACME Inc."}; var Janitor = Object.create(Employee); // Janitor now looks and behaves just like its prototype, Employee Janitor.company // => "ACME Inc.", falls back to prototype.company Janitor.name = "Janitor Tim"; // Override name Janitor.tools = ["broom", "bucket"]; // Define member variable only on child Employee.name = "CEO Jane"; // Change name of prototype Janitor.name; // => Still "Janitor Tim". Overriden members unaffected by prototype changes

Simple Function Definition function add(a, b) { return a + b; }

That's Just a Way of Saying: var add = function(a, b) { return a + b; }; // Use this consistently // Helps you remember: // Functions are just variables!

An Anonymous Function... function(element) { // Do something with element }

...Can Be Sent To Another Function each(collection, function(element) { // Do something with current element });

Example: Event Handler button.onClick(function(element) { alert(«You clicked me!»); });

Sharp Edges Global variables No block s cope Semicolon insertion == operator

Properly Scoped Variable var getSmallNumber = function(){ var smallNumber = 42; // Note use of var keyword return smallNumber; };

Sloppy, Global Variable var getSmallNumber = function(){ smallNumber = 42; return smallNumber; }; // Missing var prefix = smallNumber gets global scope // Becomes available for all code // Sticks around and pollutes namespace

No Block Scope var x = 1; if (true) { var x = 123; } // x => 123

Semicolon insertion Don't force the browser to guess!

Example a = b + c (d + e).print() becomes... a = b + c(d + e).print();

Quiz '' == '0' // true or false? 0 == '' // true or false? 0 == '0' // true or false? false == 'false' // true or false? false == '0' // true or false? false == undefined // true or false? false == null // true or false? null == undefined // true or false? ' \t\r\n ' == 0 // true or false?

How Many Did You Get? '' == '0' // false 0 == '' // true 0 == '0' // true false == 'false' // false false == '0' // true false == undefined // false false == null // false null == undefined // true ' \t\r\n ' == 0 // true // Why? Type coercion on right operand, that's why.

Instead, Use === (And !==) '' === '0' // false 0 === '' // false 0 === '0' // false false === 'false' // false false === '0' // false false === undefined // false false === null // false null === undefined // false ' \t\r\n ' === 0 // false

Advanced Stuff Closures Modules Memoization

<TABLE> <TBODY> <TR> <TD>Shady Grove</TD> <TD>Aeolian</TD> </TR> <TR> <TD>Over the River, Charlie</TD> <TD>Dorian</TD> </TR> </TBODY> </TABLE>

DOM Scripting Basics x.getElementById(id) ; // get the element with a specified id x.getElementsByTagName(name); // get all elements with a // specified tag name x.appendChild(node); // insert a child node to x x.removeChild(node), // remove a child node from x x.innerHTML = «<p>New text</p>»; // fill element with html or text

DOM Api: Crossbrowser Headache http://www.quirksmode.org

Instant Win: Crossbrowser Non-verbose Traverse DOM Manipulate DOM

Lots of Other Stuff, Too Server communication UI widgets and effects each(), map(), etc JSON parsing +++

jQuery Function $() // Short form jQuery() // Long form

Find Stuff $(“p”); // Find all paragraphs $(“#shoppingList”); // Find element with id 'shoppingList' $(“.shoppingListItem”); // Find elements with class 'shoppingListItem' $(“:text”); // Find all text elements $(“:visible”); // Find only visible elements

$() Wraps and Returns Matching Element(s)

Manipulate Matched DOM Elements $(“p”).css(”color”, ”green”); // Set color on all paragraph elements $(“p”).hide(); // Hide all paragraphs // Make all input buttons react to mouse clicks $(“input”).click(function(){ alert(”You clicked this button!”); });

Chaining Every API call returns jQuery object So we can chain function calls together “Fluent API”

Chaining Example // Set color on all paragraph elements, then hide them all $(“p”).css(”color”, ”green”).hide();

Caution! Use frameworks as needed But don't depend on them! JavaScript != jQuery

Good Practices jsLint Automated testing Unobtrusive JavaScript

Automated Testing YUI Test demo

Unobtrusive JavaScript Structure vs behavior Separate js files Event handler setup Namespaces Universal Access

Namespace Hygiene All your code within single object

Universal Access Can all your users use your site? Users without JS? Blind users with screen readers? Use progressive enhancement

Crossbrowser Dev Process Frameworks > raw DOM Test early, test often Clean, disciplined code

What Did We Cover Today? Language basics Html scripting Good practices Tools

What´s Missing? Server Communication Performance Security Practice practice practice!

Web Resources http://javascript.crockford.com http://cjohansen.no/javascript http://developer.yahoo.com/yui/theater http://ajaxian.com

Best Way to Learn: Start Building! http://ajaxian.com/archives/writing-a-javascript-tetris-lessons-learned-from-a-ruby-chap

Download This Workshop http://kjeldahlnilsson.net/jsnh.zip Slides, lecture notes, exercises Creative Commons license Use and distribute freely... ...or have me present it for you on-site :)

Contact Info [email_address] linkedin.com/in/thomaskjeldahlnilsson twitter.com/thomanil

JavaScript Needn't Hurt!

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