JavaScript_Succinctly

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Chapter 9 The Head/Global Object Conceptual overview of the head object JavaScript code itself must be contained within an object. For example, when crafting JavaScript code for a web browser environment, JavaScript is contained and executed within the window object. This window object is considered to be the "head object," or sometimes confusingly referred to as "the global object." All implementations of JavaScript require the use of a single head object. The head object is set up by JavaScript behind the scenes to encapsulate user-defined code and to house the native code with which JavaScript comes prepackaged. Userdefined code is placed by JavaScript inside the head object for execution. Let's verify this as it pertains to a web browser. In the following sample, I am creating some JavaScript values and verifying the values are placed in the head window object. Sample: sample64.html var myStringVar = 'myString'; var myFunctionVar = function () { }; myString = 'myString'; myFunction = function () { }; console.log('myStringVar' in window); // Returns true. console.log('myFunctionVar' in window); // Returns true. console.log('myString' in window); // Returns true. console.log('myFunction' in window); // Return true. You should always be aware that when you write JavaScript, it will be written in the context of the head object. The remaining material in this chapter assumes you are aware that the term "head object" is synonymous with "global object." Notes The head object is the highest scope/context available in a JavaScript environment. 78
Global functions contained within the head object JavaScript ships with some predefined functions. The following native functions are considered methods of the head object (e.g., in a web browser, window.parseInt('500')). You can think of these as ready-to-use functions and methods (of the head object) provided by JavaScript. decodeURI() decodeURIComponent() encodeURI() encodeURIComponent() eval() isFinite() isNaN() parseFloat() parseInt() The head object vs. global properties and global variables Do not confuse the head object with global properties or global variables contained within the global scope. The head object is an object that contains all objects. The term "global properties" or "global variables" is used to refer to values directly contained inside the head object and are not specifically scoped to other objects. These values are considered global because no matter where code is currently executing, in terms of scope, all code has access (via the scope chain) to these global properties and variables. In the following sample, I place a foo property in the global scope, then access this property from a different scope. Sample: sample65.html var foo = 'bar'; // foo is a global object and a property of the head/window object. var myApp = function () { // Remember functions create scope. var run = function () { 79
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By Cody Lindley Foreword by Daniel
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Table of Contents About the Author
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Object() object instance properties
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The Story behind the Succinctly Ser
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About the Author Cody Lindley is a
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Advanced technical books written ab
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“Consider that the cody object cr
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Chapter 1 JavaScript Objects Creati
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Using JavaScript, the getGender met
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* The String() constructor function
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new object that is returned from th
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Notes The Math object is the oddbal
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In this snippet, we created a new s
Page 28 and 29: Verify that literals are created fr
Page 30 and 31: The primitive values null, undefine
Page 32 and 33: The concept to take away here is th
Page 34 and 35: * This will throw an error and not
Page 36 and 37: copied, but not the actual value. T
Page 38 and 39: Sample: sample21.html // Primitive
Page 40 and 41: Notes Careful! If you mutate the na
Page 42 and 43: console.log(instanceOfCustomObject.
Page 44 and 45: myObject.prop = 'test'; myArray.pro
Page 46 and 47: Chapter 2 Working with Objects and
Page 48 and 49: Sample: sample31.html // Encapsula
Page 50 and 51: cody['getGender']() // Just slap th
Page 52 and 53: een defined. You might think that b
Page 54 and 55: console.log(myArray.toLocaleString(
Page 56 and 57: Sample: sample44.html var cody = {
Page 58 and 59: Sometimes a web browser manufacture
Page 60 and 61: I like this library because it take
Page 62 and 63: console.log(stringObject); // Logs
Page 64 and 65: Chapter 4 Number() Conceptual overv
Page 66 and 67: NEGATIVE_INFINITY POSITIVE_INFINIT
Page 68 and 69: Parameter passed to Boolean() = Mat
Page 70 and 71: console.log(Boolean(Math)); console
Page 72 and 73: var numberObject = new Number(1.100
Page 74 and 75: Chapter 7 Null Conceptual overview
Page 76 and 77: Chapter 8 Undefined Conceptual over
Page 80 and 81: object. } // Logs bar, foo's value
Page 82 and 83: Make sure you understand that the h
Page 84 and 85: Object() parameters The Object() co
Page 86 and 87: Sample: sample72.html var cody = n
Page 88 and 89: Logs 'foo', being found at Object.p
Page 90 and 91: Sample: sample77.html var addFunct
Page 92 and 93: Sample: sample79.html var yelp = f
Page 94 and 95: parameters when defining the functi
Page 96 and 97: Notes The arguments.length property
Page 98 and 99: Invoking a function (function, meth
Page 100 and 101: Self-invoking anonymous function st
Page 102 and 103: the bar variable. All this is to sh
Page 104 and 105: Chapter 12 The this Keyword Concept
Page 106 and 107: Clearly, the value of this is based
Page 108 and 109: Working around the nested function
Page 110 and 111: What you need to learn here is that
Page 112 and 113: var john = new Person(); // No argu
Page 114 and 115: Notes An unlimited number of functi
Page 116 and 117: } (); How is the value of sayHiTex
Page 118 and 119: var parentFunction = function () {
Page 120 and 121: Chapter 14 Function Prototype Prope
Page 122 and 123: Sample: sample119.html var myFunct
Page 124 and 125: In this example, the foo property i
Page 126 and 127: console.log(FooInstance.constructor
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Providing a new object as the proto
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var chuck = new Person(0, 0); conso
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An Array() is just a special type o
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It is more common to see an array d
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console.log(myArray.length); // Log
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while (myArrayLength--) { // If len
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ceil() cos() exp() floor() log() ma
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That is: a complex value is equal t
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JavaScript_Succinctly

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