book

JavaScript Enlightenment

by Cody Lindley

December 2012

Beginner

164 pages

3h 15m

English

O'Reilly Media, Inc.

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IntroductionWhy Did I Write This Book?Who Should Read This Book?Why JavaScript 1.5 and ECMAScript 3 Edition?Why Didn’t I Cover the Date(), Error(), and RegEx() Objects?More Code, Fewer WordsExhaustive Code and RepetitionColor-Coding ConventionsjsFiddle, JS Bin, and Firebug lite-devConventions Used in This BookUsing Code ExamplesSafari® Books OnlineHow to Contact UsAbout the AuthorAbout the Technical EditorsMichael RichardsonKyle SimpsonNathan SmithBen NadelRyan FlorenceNathan Logan
Creating ObjectsJavaScript Constructors Construct and Return Object InstancesThe JavaScript Native/Built-In Object ConstructorsUser-Defined/Non-Native Object Constructor FunctionsInstantiating Constructors Using the new OperatorCreating Shorthand/Literal Values from ConstructorsPrimitive (a.k.a. Simple) ValuesThe Primitive Values null, undefined, “string”, 10, true, and false Are Not ObjectsHow Primitive Values Are Stored/Copied in JavaScriptPrimitive Values Are Equal by ValueThe String, Number, and Boolean Primitive Values Act Like Objects When Used Like ObjectsComplex (a.k.a. Composite) ValuesHow Complex Values Are Stored/Copied in JavaScriptComplex Objects Are Equal by ReferenceComplex Objects Have Dynamic PropertiesThe typeof Operator Used on Primitive and Complex ValuesDynamic Properties Allow for Mutable ObjectsAll Constructor Instances Have Constructor Properties that Point to Their Constructor FunctionVerify that an Object Is an Instance of a Particular Constructor FunctionAn Instance Created From a Constructor Can Have Its Own Independent Properties (Instance Properties)The Semantics of “JavaScript Objects” and “Object() Objects”
Complex Objects Can Contain Most of the JavaScript Values as PropertiesEncapsulating Complex Objects in a Programmatically Beneficial WayGetting/Setting/Updating an Object’s Properties Using Dot Notation or Bracket NotationDeleting Object PropertiesHow References to Object Properties Are ResolvedUsing hasOwnProperty, Verify That an Object Property Is Not From the Prototype ChainChecking If an Object Contains a Given Property Using the in OperatorEnumerate (Loop Over) an Object’s Properties using the for in LoopHost Objects versus Native ObjectsEnhancing and Extending Objects with Underscore.js
Conceptual Overview of Using Object() ObjectsObject() ParametersObject() Properties and MethodsObject() Object Instance Properties and MethodsCreating Object() Objects Using “Object Literals”All Objects Inherit From Object.prototype
Conceptual Overview of Using Function() ObjectsFunction() ParametersFunction() Properties and MethodsFunction Object Instance Properties and MethodsFunctions Always Return a ValueFunctions Are First-Class Citizens (Not Just Syntax but Values)Passing Parameters to a Functionthis and arguments Values Available To All FunctionsThe arguments.callee PropertyThe Function Instance length Property and arguments.lengthRedefining Function ParametersReturn a Function Before It Is Done (Cancel Function Execution)Defining a Function (Statement, Expression, or Constructor)Invoking a Function [Function, Method, Constructor, or call() and apply()]Anonymous FunctionsSelf-Invoking Function ExpressionSelf-Invoking Anonymous Function StatementsFunctions Can Be NestedPassing Functions to Functions and Returning Functions from FunctionsInvoking Function Statements Before They Are Defined (Function Hoisting)A Function Can Call Itself (Recursion)
Conceptual Overview of the Head ObjectGlobal Functions Contained Within the Head ObjectThe Head Object versus Global Properties and Global VariablesReferring to the Head ObjectThe Head Object Is Implied and Typically Not Referenced Explicitly
Conceptual Overview of this and How It Refers to ObjectsHow Is the Value of this Determined?The this Keyword Refers to the Head Object in Nested FunctionsWorking Around the Nested Function Issue by Leveraging the Scope ChainControlling the Value of this Using call() or apply()Using the this Keyword Inside a User-Defined Constructor FunctionThe this Keyword Inside a Prototype Method Refers to a Constructor Instance
Conceptual Overview of JavaScript ScopeJavaScript Does Not Have Block ScopeUse var Inside Functions to Declare Variables and Avoid Scope GotchasThe Scope Chain (Lexical Scoping)The Scope Chain Lookup Returns the First Found ValueScope Is Determined During Function Definition, not InvocationClosures Are Caused by the Scope Chain
Conceptual Overview of the Prototype ChainWhy Care About the prototype Property?Prototype Is Standard on All function() InstancesThe Default prototype Property Is an Object() ObjectInstances Created From a Constructor Function are Linked to the Constructor’s prototype PropertyLast Stop in the prototype Chain is Object.prototypeThe prototype Chain Returns the First Property Match It Finds in the ChainReplacing the prototype Property with a New Object Removes the Default Constructor PropertyInstances That Inherit Properties from the Prototype Will Always Get the Latest ValuesReplacing the prototype Property with a New Object Does Not Update Former InstancesUser-Defined Constructors Can Leverage the Same Prototype Inheritance as Native ConstructorsCreating Inheritance Chains (the Original Intention)
Conceptual Overview of Using Array() ObjectsArray() ParametersArray() Properties and MethodsArray Object Instance Properties and MethodsCreating ArraysAdding and Updating Values in ArraysLength versus IndexDefining Arrays with a Predefined LengthSetting Array Length can Add or Remove ValuesArrays Containing Other Arrays (Multidimensional Arrays)Looping Over an Array, Backwards and Forwards

Conceptual Overview of Using the String() ObjectString() ParametersString() Properties and MethodsString Object Instance Properties and Methods
Conceptual Overview of Using the Number() ObjectIntegers and Floating-Point NumbersNumber() ParametersNumber() PropertiesNumber Object Instance Properties and Methods
Conceptual Overview of Using the Boolean() ObjectBoolean() ParametersBoolean() Properties and MethodsBoolean Object Instance Properties and MethodsNon-Primitive False Boolean Objects Convert to trueCertain Things Are false, Everything Else Is true
Primitive/Literal Values Are Converted to Objects When Properties Are AccessedYou Should Typically Use Primitive String, Number, and Boolean Values
Conceptual Overview of Using the null Valuetypeof Returns null Values as “object”
Conceptual Overview of the undefined ValueJavaScript ECMAScript 3 Edition (and Later) Declares the undefined Variable in the Global Scope
Conceptual Overview of the Built-In Math ObjectMath Properties and MethodsMath Is Not a Constructor FunctionMath Has Constants You Cannot Augment/Mutate

Overview

If you’re an advanced beginner or intermediate JavaScript developer, JavaScript Enlightenment will solidify your understanding of the language—especially if you use a JavaScript library. In this concise book, JavaScript expert Cody Lindley (jQuery Cookbook) provides an accurate view of the language by examining its objects and supporting nuances.

Libraries and frameworks help you build web applications quickly and efficiently, but when things go wrong or performance becomes an issue, knowing how and why they work is critical. If you’re ready to go under the hood and get your hands dirty with JavaScript internals, this is your book.

Get a short and digestible summary of ECMA-262, Edition 3, backed by real code you can run instantly
Examine the creation of JavaScript objects
Learn complex values, primitive values, scope, and inheritance
Understand the importance of the head object
Work with string, number, and Boolean objects and values
Discover how to use the null value and the built-in math object
Get into the details—beyond Mozilla’s reference guide for JavaScript 1.5