A practical walkthrough of using map/reduce with MongoDB to aggregate statistics for generating a report.
Addy Osmani introduces backbone.js as one part of the toolkit for building mobile JavaScript web applications. Backbone is an MVC-like framework to structure your application, simplifies server-side persistence, decouples the DOM from data, succinctly separates apps into Models, views and routers and provides synchronisation between DOM, model and collections.
Klaus Komenda takes us through the history of development patterns of JavaScript demonstrating the pros and cons. Taking a typical JavaScript feature he starts with the old-school global functions method and iterates through a Singleton, Module Pattern, Revealing Module Pattern, Custom Objects and Lazy Function Definitions bringing the same feature up-to-date.
Ben Cherry, web developer at Twitter, takes us step by step through the Module Pattern. He introduces the standard features of Anonymous Closures and avoiding global scope, and covers advanced concepts such as augmentation, cloning, inheritance, private state and sub-modules.
A simplified explanation of closures by Morris Johns: A closure is the local variables for a function - kept alive after the function has returned.
Mike Alsup builds up to an elegant plugin development pattern for jQuery plugins, starting with requirements and adding a piece at a time. By explaining the reasoning and though behind each piece of the puzzle, it explains a number of important good parts of the JavaScript language
Fellow co-worker Lawrence Carvalho discusses the Undo functionality, and as web based applications start to replace desktop ones, this crucial bit of functionality will become expected by application users. Lawrence talks about the Memento design pattern and guides us through designing objects that can undo their changes. He builds an undoable text widget.
Cory Hudson sees callbacks as benefiting from currying JavaScript functions, and defines currying as turning a function with two arguments into a function with one argument that returns a function of one argument. He starts off with two functions and shows how to combine them into one curried function, and also builds a generic version. He shows a good usage of a curried function in an array map() function, which is similar to Prototype's bind().
Jonathan Snook demonstrates when JavaScript passes by reference or passes by value. Essentially, primitive types are passed by value, objects are passed by reference. Passing functions however, makes things look like a pass by value if the this keyword is being used in the code. Snook offers workarounds to this by passing objects so that the context is correct, or using the call() function to ensure the context is correct.
Dan Webb describes curried functions as a way of creating reusable callback functions for event handlers or Ajax requests, or anything that takes a function as an argument. By using closures, curried functions have a simple way of persisting data between calls. He also offers an elegant way of running a lots of methods on objects, with a simple map function written as a curried function.
Svend Tofte discussed currying JavaScript functions, which he describes as a way to partially evaluate functions. Its a function that returns another function. In an example, one function either adds together two numbers, or if only one parameter is sent, returns a function that can be called later to supply the second number.
Tim describes another two different approaches to using the Module Pattern (a way of creating Singletons). The first example takes advantage of the natural indentation to clearly see which methods are private and which are public. The second is a curried function, a function that returns another function.
Christian Heilmann offers another incremental improvement to the Module Pattern, and calls it the Revealing Module Pattern. This defines an anonymous object that contains a list of methods and properties that are publicly available. Christian notes that this method also allows you to set up a public property that's privately generated by a method. Christian's improvement makes it quickly clear which properties and methods are public.
Christian Heilmann compares the Object Literal to Douglas Crockford's Module pattern and finds that the Module pattern fixes a major problem of the object literal - the difficult choice of using this or fully qualified references to functions in the same block. Christian also covers the improvements in the Module Pattern, like the decluttering of the return block, which makes the resulting a little easier to work with.
Klaus Komenda discusses a number of ways of encapsulating JavaScript functions into objects and namespaces, and shows how to use each pattern. He covers Singletons, Douglas Crockford's Module Pattern and Custom Objects, building the same functionality with each technique.
An online copy of O'Reilly's 2002 book Creating Applications with Mozilla. It focused on pre-1.0 versions of Mozilla, so details about the application structure has changed, but the XUL elements are relatively stable.
All JavaScript implementations implement a debugger statement, which can be called at any point in your script. Also we have console.debug in Firebug.
Douglas Crockford's JavaScript code conventions. Covers indentation, line length, comments, variable and function declarations, minification, statements and labels, whitespace, scope and eval.
Instead of creating a new XmlHttpRequest object for every request, this post provides code to pool these objects together and reuse them. This saves a great deal of processing times, particularly in IE.
An example of a Decorator pattern based on the flexibility of prototype to extend a JavaScript object. Decorating an object allows customised functions to be called before and after a method call, the real method call is wrapped between the before and after hooks. One method of Aspect-oriented programming with JavaScript
Christian Heilmann offers us Dishy, a JavaScript REST API for talking to del.icio.us. Taking full advantage of del.icio.us' JSON format and the script element, Dishy doesn't need a server-side proxy. Its a useful helper class for easily getting information from del.icio.us.
Christian Heilmann's excellent guide to writing unobtrusive JavaScript. Takes the reader from the inline JavaScript world right through to a clean dynamically attached events with all the JavaScript code in external files. Covers DOM Scripting. This is the key reference to unobtrusive scripting.
Douglas Crockford discusses his method of exposing the powerful prototypal inheritance from JavaScript, using his object function which untangles JavaScript's classical-adopted constructor pattern.
Gez Lemon reviews Christian Heilmann's recently published book. Its a thumbs up, and recommended for developers working with standards and accessibility, regardless of their JavaScript level.
As well as supporting CSS based selectors, jQuery also supports XPath expressions. This page lists a plethora of code snippets demonstrating jQuery's XPath matching capabilities.