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Once again, prototyping can help us implement an OOP feature in a more elegant way than when using closures. Prototype-based inheritance makes use of the behavior of JavaScript prototypes. When accessing a member of a function, that member will be looked for in the function itself. If it's not found there, the member is looked for in the function's prototype. If it's still not found, the member is looked for in the prototype's prototype, and so on until the prototype of the implicit Object object.
Updated: 01/11/2008
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There are two significant techniques for implementing the OOP concept of inheritance with JavaScript code. The first technique uses closures, and the other technique makes use of a feature of the language named prototyping. Early implementations of the Microsoft AJAX library made use of closures-based inheritance, and in the final stage the code was rewritten to use prototypes. In the following few pages we'll quickly discuss both techniques.
Updated: 01/11/2008
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JavaScript Execution Context In this section we'll take a peek under the hood of the JavaScript closures and the mechanisms that allow us to create classes, objects, and object members in JavaScript. For most cases, understanding these mechanisms isn't absolutely necessary for writing JavaScript co...
Updated: 01/11/2008
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Creating Object Members on the Fly One major difference between OOP in C# and ASP.NET, and OOP in JavaScript, is that JavaScript allows creating object members "on the fly". This is true for objects and classes that you create yourself and also for JavaScript's own objects and types as well.
Updated: 01/11/2008
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Thinking of Objects as Associative Arrays A key element in understanding JavaScript objects is understanding the notion of associative arrays, which are nothing more than collections of (key, value) pairs. As a .NET developer you have worked with associative arrays represented by classes such as Na...
Price: Free - Updated: 01/08/2008
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C# and JavaScript Classes For the purpose of demonstrating a few more OOP-related concepts, we'll use another class. Our new class is named Table, and it has two public fields (rows, columns), and one method, getCellCount(). The getCellCount() method should return the number of rows multiplied by t...
Price: Free - Updated: 01/08/2008
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JavaScript Classes Not only can JavaScript functions contain other functions, but they can also be instantiated. This makes JavaScript functions a good candidate for implementing the concept of a class from traditional object-oriented programming. This is very helpful feature indeed, because JavaSc...
Price: Free - Updated: 01/08/2008
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Anonymous Functions Anonymous functions can be created adhoc and used instead of a named function. Although this can hinder readability when the function is more complex, you can do this if you don't intend to reuse a function's code. In the following example we pass such an anonymous function to D...
Price: Free - Updated: 01/08/2008
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Functions as Variables In JavaScript, functions are first-class objects. This means that a function is regarded as a data type whose values can be saved in local variables, passed as parameters, and so on. For example, when defining a function, you can assign it to a variable, and then call the fun...
Price: Free - Updated: 01/08/2008
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JavaScript Functions A simple fact that was highlighted in the previous chapter, but that is often overlooked, is key to understanding how objects in JavaScript work: code that doesn't belong to a function is executed when it's read by the JavaScript interpreter, while code that belongs to a functi...
Price: Free - Updated: 01/08/2008
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