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Incrementing a Binary Number Step Dec. Binary Commentary A 0 00000000 B 1 00000001 C 1 00000001 D 2 00000010 E 3 00000011 F 3 00000011 G 4 00000100 H 5 00000101 I 6 00000110 J 7 00000111 K 8 00001000 L 9 00001001 M 10 00001010 N 11 00001011 O 12 00001100 P 13 00001101 Q 14 00001110 R 15 00001111 S 16 00010000 We begin with a clean slate. This is 0 in binary and decimal. Start by switching the right-most bit to on position. Another way of thinking about it is that we shift 1 left into the number. To increment by 1, start by shifting this bit to the left. A zero to the right is now open. We just incremented the value by one. The equivalent of 00000010 in decimal is 2. Before we move on we first need to fill in remaining zeros to the right. Note that 3 isn’t 00000100. That’s a common mistake. We ran out of space. So, the next step is to move the leading 1 to the left again, and zero out everything to the right. This is 4 in decimal. The process repeats itself. It looks like we exhausted all combinations. Just like in step G, we shift left and zero out again. 11 is 1011 and not 1100 because we are always concerned with filling in the two right-most 0s first. See steps A-J. Same thing. Zero out. Shift left. Zero out. 29
What is a Variable? Variables can be thought of and used in so many different ways that it would be pointless to give them one specific definition. In the context of a computer program, what variable is can only be understood by experimenting and writing your own computer programs. A variable consists of a name and value. var x; // Create a variable but skip the value. var x = 1; // Create a variable and assign the value of 1 to it. var a = b = c = 1; // Create three variables and assign value 1 to all of them. Everything in JavaScript is an object. Therefore, all variables we can possibly create are objects. An object is a concept. An idea. An object is not stored in computer memory with 0s and 1s. It can be thought by the programmers as a theoretical structure of the program. The computer processor only sees 0s and 1s. It doesn’t care about how we think. It just does what it’s told. This means that the concept of an object doesn’t exist anywhere in the computer itself. It exists only in our head. That is how humans think - in terms of objects. It’s a part of the creative process inherent to all of us. There are objects inside other objects. Like ideas inside other ideas. So what exactly is a JavaScript variable then? Let’s put it this way. If a computer program is a novel, then a variable is a word. A function is a sentence. And a block of code that calls a number of functions is a chapter. A variable is a versatile tool which can be many things. Theorethically, it is just a name that we create as an alias to a placeholder somewhere in computer memory at a random location. This way we don’t have to memorize the actual computer address just to refer to that location in memory every time we want to do something with that variables. Once we assign a value to a variable it becomes that value. If we assign an object to a variable name then that name becomes the object. If we assign a function, it becomes a function. The value of a variable is up to the context in which that variable is used. A variable can even refer to a an object created using the JSON. So as you see, the variable name is a reference to something. A variable is determined by its value. The name of the variable is a reference to that value. A variable can also be an integer or a string. But even a number or a string is an object in JavaScript. The value of the variable is always an object. This is why sometimes it is thought that variables are objects. But it doesn’t mean that the name of the variable is an object. The name is just a reference to the address in memory where that value is stored. 30
Page 1 and 2: “ Second Revision. July 2012 Unde
Page 3 and 4: Prototype, JavaScript Objects and J
Page 5 and 6: Thought transcends matter. When we
Page 7 and 8: Preface The purpose of this book is
Page 9 and 10: A Lesson in Creativity The web deve
Page 11 and 12: I love jQuery because it allows me
Page 13 and 14: Improving Page Load Performance The
Page 15 and 16: Determining the Placement of Intern
Page 17 and 18: JavaScript 1. The only language peo
Page 19 and 20: What is JavaScript? Web designers u
Page 21 and 22: As you can see, variables can be as
Page 23 and 24: The example above will first execut
Page 25 and 26: Only variables and events should be
Page 27 and 28: Notice that variables a and b are c
Page 29 and 30: What Exactly is a JavaScript Variab
Page 31 and 32: A variable allocates enough data st
Page 33: Do you want to really understand pr
Page 37 and 38: In order to understand bitwise logi
Page 39 and 40: At first this might seem confusing.
Page 41 and 42: Let’s display the variable “a
Page 43 and 44: What’s important is the return va
Page 45 and 46: Inserting Form Values into MySQL Da
Page 47 and 48: I like code that you can “read”
Page 49 and 50: An object is created from a class.
Page 51 and 52: Dynamic Prototype-based Objects in
Page 53 and 54: Without knowing anything at all abo
Page 55 and 56: More About JSON JSON is a data inte
Page 57 and 58: In some programming languages the t
Page 59 and 60: JavaScript from scratch. If you are
Page 61 and 62: property access operator - the . (d
Page 63 and 64: Why does jQuery do exactly the same
Page 65 and 66: Learning jQuery The greatest thing
Page 67 and 68: If this sounds like you, then you w
Page 69 and 70: Web App Initialization To initializ
Page 71 and 72: In JavaScript, we can define variab
Page 73 and 74: As mentioned above, to an experienc
Page 75 and 76: Including jQuery In Your Source Cod
Page 77 and 78: Including jQuery as an External CDN
Page 79 and 80: Including jQuery UI In the Starting
Page 81 and 82: What Kind of Elements Can You Selec
Page 83: To traverse the DOM and make sure t
Page 86 and 87:
Here is a basic inline CSS example
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Because the DIV element has ID of
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After selecting all of these input
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Figure 1 Mentality of a beginner jQ
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Whose Children Are These? If we are
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Next, let’s explore the possibili
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jQuery Events Because jQuery is so
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Of course, the effects of binding a
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Using toggle() Events Toggling betw
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Speed Up Your jQuery Code jQuery is
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Let’s now look at the jQuery way
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Practical jQuery Lessons Instead of
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There is a solution to this problem
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jQuery provides a secondary way of
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Lesson 3: Callback Functions All jQ
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For example, the following statemen
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As you may know an object can conta
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Notice that when we do it this way,
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Alternatively, we can create the pa
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if (“light”.match(/darkness/) =
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jQuery and Regular Expressions In p
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This is probably as simple as it ge
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The following example will demonstr
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Making Good CSS Buttons This tutori
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Sometimes it makes sense to make th
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1. Specify javascript: return false
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Our goal is to match the button wit
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So far, we have briefly discussed t
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Note from the Author Looks like you
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