JSLint

With the advent of so many different JavaScript libraries, the question often arises, "is there one library that will meet all of my needs?" I can tell you from personal experience, the answer is almost always, "no". At some point in a full Web site or Web application build, you will need to add custom functionality.

You need only to look as far as your preferred JavaScript library to get an indication of how much JavaScript has evolved over the years. As you mature in your JavaScript knowledge, you may find yourself not only wanting to use, but also wanting to understand the core functionality inherent to each library. Deconstructing the source, you will discover common threads running through each line of code. If you can learn to imitate and manipulate these patterns to your benefit, then you will find that you have reached an important milestone.

How will you start to develop your desired features, and how will you integrate them into a production environment? If you want to gain efficiencies, then you will want to reuse code gleaned throughout aging tutorials (in Web years). This can require refactoring a fair amount of JavaScript, so that you can take advantage of fresh design patterns, evolving programming techniques, and general best practices.

In recent years, many helpful browser-based tools have hit the scene, the most popular of which are the Web Developer Toolbar and Firebug add-on extensions for Firefox. While these are indeed invaluable, the JavaScript tool I find myself using the most is Douglas Crockford’s JSLin.

JSLint after seeing numerous developers frustrated with the inherent fluidity of the syntax. Coupled with inconsistencies in browser interpretation, this loosely typed methodology can often be difficult to master. Yet, properly understood, JavaScript can be quite a powerful language.

In a nutshell, JSLint is to JavaScript what the W3C’s validators are for HTML and CSS. By cutting and pasting JavaScript code into JSLint, you can check not only for outright errors, but also for scripting best practices. Additionally, when declaring variables, JavaScript will let you get away with lazy declarations like: foobar = value. This is a bad habit, because it leaves the variable exposed in the global scope, allowing all functions have access to it. Unless that is your intention, the best way to declare a variable would be: var foobar = value.

A huge passive benefit of JSLint is that it basically forces you to write well structured code. Much like XHTML requires tighter adherence to best practices than HTML, JavaScript that passes JSLint is nearly 100% perfect. Since JavaScript is interpreted by the browser at runtime (not compiled beforehand), every last bit of optimization counts. In no other programming language is the impact on user experience so immediate.

Whether you are a JavaScript newbie or guru, I think you will agree that JSLint is a valuable weapon in any scripter’s arsenal.
Once you make JSLint a regular part of your development process, you will wonder how you ever did without.