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Learning JavaScript Object Definitions When I was learning to write programs for the PC back in late 1990s, I have chosen C++ as my first programming language. Back then, you had to understand things like the command line and knowing what IDE (Integrated Development Environment) to use. In other words, you couldn’t just type up some code into Notepad and expect Windows to execute your program. The code had to be first compiled and only then executed. This is still how compiled languages like C++ work today. But HTML and JavaScript are much more accessible. In fact, their popularity among web programmers can be accredited to how easy it is to get started with them. The browser does the compiling and execution of your program. You just write the code. In order to run a C++ application on a Windows computer, the program has to be first compiled, built into an executable file that the Operating System understands and then launched by executing the file. The browser such as Internet Explorer, Firefox and Chrome are all examples of a desktop application that was compiled and built into an executable file first. When you click on its icon to launch the browser, you are executing the file that has been built by developers of the browser. But JavaScript and HTML code run directly inside the browser. There is nothing to compile or build. The program executes after it is processed (compiled and built into machine code) by the browser. This makes it incredibly easy for anyone to start writing JavaScript code. But that can be dangerous. Very often people jump into memorizing what a line of code looks like from online tutorials and books and then try to recreate it in their own programs with different parameters. But this approach to learning a language leads to confusion in the long run because of the lack of understanding internal mechanics of a language. Even though the process of writing the code was made easy by the automatic JIT (Just In Time) compilation right inside the browser, the problem still arises when it comes to learning 53
JavaScript from scratch. If you are an absolute beginner, there are things you may not want to do. The understanding how to learn a programming language becomes important. The right way of thinking about JavaScript programming lies in understanding the creation and manipulation of computer data. In other words, variables, functions, integers, strings, arrays, etc. are the blocks of data we will define. This data will be manipulated by JavaScript statements and logical constructs we create during the period of time our program executes, in other words the run-time. One of these often overlooked concepts is the definition of objects in JavaScript. I have not seen many tutorials that actually spend time explaining this. They simply jump directly to practical examples. But in order to really get a grasp on the art of programming websites, we need to understand data creation and manipulation at the very root. We must thoroughly understand what’s going on at the very core of computer language syntax. And at the core of JavaScript there are objects and object definitions. Let’s take a look at an object definition from one of my previous tutorials, the LightBulb object: var LightBulb = { shape: 0, socket_type: “European”, state: 0, turn_on: function() { /* code that turns bulb on here */ }, turn_off: function() { /* code that turns bulb off here */ } }; Notice how we still use the var keyword to define an object, not a variable. This can actually be thought of as a flaw in the language design as it surely can confuse us. Is it a variable, or is it an object? Let’s analyze this structure in a slightly different way. Thinking of code using visual imagination, we can draw this diagram: 54
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“ Second Revision. July 2012 Unde
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Prototype, JavaScript Objects and J
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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 and 34: Do you want to really understand pr
Page 35 and 36: What is a Variable? Variables can b
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: In some programming languages the t
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
Page 88 and 89: Because the DIV element has ID of
Page 90 and 91: After selecting all of these input
Page 92 and 93: Figure 1 Mentality of a beginner jQ
Page 94 and 95: Whose Children Are These? If we are
Page 96 and 97: Next, let’s explore the possibili
Page 98 and 99: jQuery Events Because jQuery is so
Page 100 and 101: Of course, the effects of binding a
Page 102 and 103: Using toggle() Events Toggling betw
Page 104 and 105: Speed Up Your jQuery Code jQuery is
Page 106 and 107: 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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