JavaScript_Succinctly

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Chapter 7 Null Conceptual overview of using the null value You can use null to explicitly indicate that an object property does not contain a value. Typically, if a property is set up to contain a value, but the value is not available for some reason, the value null should be used to indicate that the reference property has an empty value. Sample: sample60.html // The property foo is waiting for a value, so we set its initial value to null. var myObjectObject = { foo: null }; console.log(myObjectObject.foo); // Logs 'null'. Notes Don't confuse null with undefined. undefined is used by <strong>JavaScript</strong> to tell you that something is missing. null is provided so you can determine when a value is expected but not available yet. typeof returns null values as "object" For a variable that has a value of null, the typeof operator returns "object”. If you need to verify a null value, the ideal solution would be to see if the value you are after is equal to null. In the following sample, we use the === operator to specifically verify that we are dealing with a null value. Sample: sample61.html var myObject = null; console.log(typeof myObject); // Logs 'object', not exactly helpful. console.log(myObject === null); // Logs true, only for a real null value. 74
75 Notes When verifying a null value, always use === because == does not distinguish between null and undefined.
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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
Page 24 and 25: Notes The Math object is the oddbal
Page 26 and 27: 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 76 and 77: Chapter 8 Undefined Conceptual over
Page 78 and 79: Chapter 9 The Head/Global Object Co
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
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In this example, the foo property i
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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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