You are previewing JavaScript Patterns.

JavaScript Patterns

Cover of JavaScript Patterns by Stoyan Stefanov Published by O'Reilly Media, Inc.
  1. JavaScript Patterns
  2. Dedication
  3. Preface
    1. Target Audience
    2. Conventions Used in This Book
    3. Using Code Examples
    4. Safari® Books Online
    5. How to Contact Us
    6. Acknowledgments
    7. Credits
    8. Reading
  4. 1. Introduction
    1. Patterns
    2. JavaScript: Concepts
      1. Object-Oriented
      2. No Classes
      3. Prototypes
      4. Environment
    3. ECMAScript 5
    4. JSLint
    5. The Console
  5. 2. Essentials
    1. Writing Maintainable Code
    2. Minimizing Globals
      1. The Problem with Globals
      2. Side Effects When Forgetting var
      3. Access to the Global Object
      4. Single var Pattern
      5. Hoisting: A Problem with Scattered vars
    3. for Loops
    4. for-in Loops
    5. (Not) Augmenting Built-in Prototypes
    6. switch Pattern
    7. Avoiding Implied Typecasting
    8. Avoiding eval()
    9. Number Conversions with parseInt()
    10. Coding Conventions
      1. Indentation
      2. Curly Braces
      3. Opening Brace Location
      4. White Space
    11. Naming Conventions
      1. Capitalizing Constructors
      2. Separating Words
      3. Other Naming Patterns
    12. Writing Comments
    13. Writing API Docs
      1. YUIDoc Example
    14. Writing to Be Read
    15. Peer Reviews
    16. Minify…In Production
    17. Run JSLint
    18. Summary
  6. 3. Literals and Constructors
    1. Object Literal
      1. The Object Literal Syntax
      2. Objects from a Constructor
      3. Object Constructor Catch
    2. Custom Constructor Functions
      1. Constructor’s Return Values
    3. Patterns for Enforcing new
      1. Naming Convention
      2. Using that
      3. Self-Invoking Constructor
    4. Array Literal
      1. Array Literal Syntax
      2. Array Constructor Curiousness
      3. Check for Array-ness
    5. JSON
      1. Working with JSON
    6. Regular Expression Literal
      1. Regular Expression Literal Syntax
    7. Primitive Wrappers
    8. Error Objects
    9. Summary
  7. 4. Functions
    1. Background
      1. Disambiguation of Terminology
      2. Declarations Versus Expressions: Names and Hoisting
      3. Function’s name Property
      4. Function Hoisting
    2. Callback Pattern
      1. A Callback Example
      2. Callbacks and Scope
      3. Asynchronous Event Listeners
      4. Timeouts
      5. Callbacks in Libraries
    3. Returning Functions
    4. Self-Defining Functions
    5. Immediate Functions
      1. Parameters of an Immediate Function
      2. Returned Values from Immediate Functions
      3. Benefits and Usage
    6. Immediate Object Initialization
    7. Init-Time Branching
    8. Function Properties—A Memoization Pattern
    9. Configuration Objects
    10. Curry
      1. Function Application
      2. Partial Application
      3. Currying
      4. When to Use Currying
    11. Summary
  8. 5. Object Creation Patterns
    1. Namespace Pattern
      1. General Purpose Namespace Function
    2. Declaring Dependencies
    3. Private Properties and Methods
      1. Private Members
      2. Privileged Methods
      3. Privacy Failures
      4. Object Literals and Privacy
      5. Prototypes and Privacy
      6. Revealing Private Functions As Public Methods
    4. Module Pattern
      1. Revealing Module Pattern
      2. Modules That Create Constructors
      3. Importing Globals into a Module
    5. Sandbox Pattern
      1. A Global Constructor
      2. Adding Modules
      3. Implementing the Constructor
    6. Static Members
      1. Public Static Members
      2. Private Static Members
    7. Object Constants
    8. Chaining Pattern
      1. Pros and Cons of the Chaining Pattern
    9. method() Method
    10. Summary
  9. 6. Code Reuse Patterns
    1. Classical Versus Modern Inheritance Patterns
    2. Expected Outcome When Using Classical Inheritance
    3. Classical Pattern #1—The Default Pattern
      1. Following the Prototype Chain
      2. Drawbacks When Using Pattern #1
    4. Classical Pattern #2—Rent-a-Constructor
      1. The Prototype Chain
      2. Multiple Inheritance by Borrowing Constructors
      3. Pros and Cons of the Borrowing Constructor Pattern
    5. Classical Pattern #3—Rent and Set Prototype
    6. Classical Pattern #4—Share the Prototype
    7. Classical Pattern #5—A Temporary Constructor
      1. Storing the Superclass
      2. Resetting the Constructor Pointer
    8. Klass
    9. Prototypal Inheritance
      1. Discussion
      2. Addition to ECMAScript 5
    10. Inheritance by Copying Properties
    11. Mix-ins
    12. Borrowing Methods
      1. Example: Borrow from Array
      2. Borrow and Bind
      3. Function.prototype.bind()
    13. Summary
  10. 7. Design Patterns
    1. Singleton
      1. Using new
      2. Instance in a Static Property
      3. Instance in a Closure
    2. Factory
      1. Built-in Object Factory
    3. Iterator
    4. Decorator
      1. Usage
      2. Implementation
      3. Implementation Using a List
    5. Strategy
      1. Data Validation Example
    6. Façade
    7. Proxy
      1. An Example
      2. Proxy As a Cache
    8. Mediator
      1. Mediator Example
    9. Observer
      1. Example #1: Magazine Subscriptions
      2. Example #2: The Keypress Game
    10. Summary
  11. 8. DOM and Browser Patterns
    1. Separation of Concerns
    2. DOM Scripting
      1. DOM Access
      2. DOM Manipulation
    3. Events
      1. Event Handling
      2. Event Delegation
    4. Long-Running Scripts
      1. setTimeout()
      2. Web Workers
    5. Remote Scripting
      1. XMLHttpRequest
      2. JSONP
      3. Frames and Image Beacons
    6. Deploying JavaScript
      1. Combining Scripts
      2. Minifying and Compressing
      3. Expires Header
      4. Using a CDN
    7. Loading Strategies
      1. The Place of the <script> Element
      2. HTTP Chunking
      3. Dynamic <script> Element for Nonblocking Downloads
      4. Lazy-Loading
      5. Loading on Demand
      6. Preloading JavaScript
    8. Summary
  12. Index
  13. About the Author
  14. Colophon
  15. Copyright
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Chapter 8. DOM and Browser Patterns

In the previous chapters of the book, the main focus was on the core JavaScript (ECMAScript) and not so much on patterns for using JavaScript in the browser. In contrast, this chapter explores a number of browser-specific patterns, because this is the most common environment for JavaScript programs. Browser scripting is also what most people have in mind when they say they don’t like JavaScript. And that’s understandable, given all the inconsistent host objects and DOM implementations that exist in the browsers. It’s obvious that we can benefit from any good practices that help make the client scripting less of a pain.

In this chapter you see some patterns divided into several areas, including DOM scripting, event handling, remote scripting, strategies for loading JavaScript on the page, and steps to deploying JavaScript to production websites.

But first, let’s start with a brief and somewhat philosophical discussion on how to approach client-side scripting.

Separation of Concerns

The three main concerns in web application development are:

Content

The HTML document

Presentation

The CSS styles that specify how the document looks

Behavior

The JavaScript, which handles the user interaction and any dynamic changes to the document

Keeping the three concerns as separate as possible improves the delivery of the application to a vast array of user agents—graphic browsers, text-only browsers, assistive technology for disabled users, mobile devices, and so on. The ...

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