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Javascript Closures

Javascript Closures
Introduction Closure A "closure" is an expression (typically a function) that can have free variables together with an environment that binds those variables (that "closes" the expression). Closures are one of the most powerful features of ECMAScript (javascript) but they cannot be property exploited without understanding them. They are, however, relatively easy to create, even accidentally, and their creation has potentially harmful consequences, particularly in some relatively common web browser environments. To avoid accidentally encountering the drawbacks and to take advantage of the benefits they offer it is necessary to understand their mechanism. This depends heavily on the role of scope chains in identifier resolution and so on the resolution of property names on objects. The simple explanation of a Closure is that ECMAScript allows inner functions; function definitions and function expressions that are inside the function bodes of other functions. Assignment of Values Finally:- An

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Truth, Equality and JavaScript You don’t have to be a JavaScript novice to get confused by this… or this… The good news is that there is a standard and all browsers follow it. Some authors will tell you to fear coercion and and code against it. I hope to persuade you that coercion is a feature to be leveraged (or at the very least understood), not avoided… Is x true? Does x equal y?

Exception Handling in ASP.NET MVC Index Introduction Exception handling is a serious matter in any application, whether it's web or desktop. Implementing a proper exception handling is important in any application. In most cases once we catch the exception we have to log the exception details to database or text file and show a friendly message to the user. In ASP.NET applications, error handling is done mostly in two ways: at local level using try-catch blocks and at global level using application events.

Learning JavaScript Design Patterns Design patterns are reusable solutions to commonly occurring problems in software design. They are both exciting and a fascinating topic to explore in any programming language. One reason for this is that they help us build upon the combined experience of many developers that came before us and ensure we structure our code in an optimized way, meeting the needs of problems we're attempting to solve. Design patterns also provide us a common vocabulary to describe solutions. This can be significantly simpler than describing syntax and semantics when we're attempting to convey a way of structuring a solution in code form to others. In this book we will explore applying both classical and modern design patterns to the JavaScript programming language.

Towards Reusable Charts I’d like to propose a convention for encapsulating reusable charts in D3. Wait for it… function chart() { } A function; the standard unit of code reuse! #Configuration I jest; not any function will do. JavaScript Scoping and Hoisting Do you know what value will be alerted if the following is executed as a JavaScript program? var foo = 1; function bar() { if (!foo) { var foo = 10; } alert(foo); } bar(); If it surprises you that the answer is “10”, then this one will probably really throw you for a loop: var a = 1; function b() { a = 10; return; function a() {} } b(); alert(a);

Using Objects to Organize Your Code This is a reprint of an article that originally appeared in the March 2009 issue of JSMag. When you move beyond simple snippets of jQuery and start developing more complex user interactions, your code can quickly become unwieldy and difficult to debug. This article shows you how to start thinking about these interactions in terms of the bits of behavior the feature comprises, using the object literal pattern.

Cloning the RepRap Prusa The grounbreaking research/hacking team at The University of Washington’s Solheim lab have begun cloning RepRaps. The RepRap project is a project that aims to make an open source self-replicating 3D printer. If sucessful this would make 3D printers available for the cost of the materials alone. At the Solheim Lab the Open3DP project is undertaking lots of research to support open 3D printing innitiatives. They have just now annouced that they can produce all the plastic parts for the Prusa Mendel in 30 minutes using molding. JavaScript Garden Although JavaScript deals fine with the syntax of two matching curly braces for blocks, it does not support block scope; hence, all that is left in the language is function scope. function test() { // a scope for(var i = 0; i < 10; i++) { // not a scope // count } console.log(i); // 10} There are also no distinct namespaces in JavaScript, which means that everything gets defined in one globally shared namespace. Each time a variable is referenced, JavaScript will traverse upwards through all the scopes until it finds it. In the case that it reaches the global scope and still has not found the requested name, it will raise a ReferenceError. The Bane of Global Variables

Compiling MVC Views In A Build Environment ASP.NET MVC project templates include support for precompiling views, which is useful for finding syntax errors within your views at build time rather than at runtime. In case you missed the memo, the following outline how to enable this feature. Right click on your ASP.NET MVC project in the Solution Explorer Select Unload Project in the context menu. Your project will show up as unavailable