Ah, JavaScript...we all love to hate it. But the fact is that JavaScript is one of the most popular programming languages in the world and its widespread use will continue to grow with the increased use of popular JavaScript libraries like jQuery. It is the language of the web. JScript, Microsoft's implementation (really just a different name) of JavaScript, is an integral part of developing and extending the capabilities of MS CRM. CRM 2011 is particularly geared toward the extended use of JavaScript with the inclusion of web resources and the REST endpoint/Odata web service architecture. The recommended (and provided SDK samples) interaction with the new REST endpoint is with the jQuery library and using JSON formatted data, both of which are JavaScript based.
Given this popular and ever growing use, there are a few (many actually) things that should be taken into consideration when writing JavaScript code. Douglas Crockford provides an extensive and in-depth discussion of these items in his book "JavaScript: The Good Parts". I would highly recommend this book for anyone who works with JavaScript frequently. One of my favorite quotes from the book is this:
"The amazing thing about JavaScript is that it is possible to get work done with it
without knowing much about the language, or even knowing much about programming."
But this ease of use doesn't necessarily mean that the code will be consistently reliable or will be using best practices. This is very true with its use in MS CRM...there is plenty of information available on the web and just about anyone can copy-n-paste a code snippet or two and bam you are programming! But there are risks with proceeding this way, as there are many code samples out there that may not be written with best practices in mind. To help mitigate this risk, I would like to discuss a couple easy items that can help clean up your JavaScript and may save time troubleshooting and tracking down mysterious issues.
Here's a couple key points that I'd like to talk about to get you started with better JavaScript code:
- Declaring variables, not using the var keyword
Common practice (at least sometimes):
Best practice:
- var myVariable = "Jerry";
Why: JavaScript lets you use a variable even when you have not explicitly declared it. However, this makes the variable a global variable, which means that it is accessible to the program outside of the scope in which it is being used. This can easily lead to naming conflicts and unintentional reassignment of a variable's value. Bottom line: always declare variables with the var keyword.
- Placement of curly braces {}:
Common formatting, especially for C# users, is to format a statement like so:
If (test)
{
//code here
}
Best practice:
If (test) {
//code here
}
Why: JavaScript will try to automatically correct and insert semicolons where it thinks they belong. In certain situations, this can yield incorrect results, like when trying to set an object's value and it is inadvertently turned into a statement when a semicolon is automatically added.
- Testing for equality and inequality
Common practice:
- != to test for inequality
Best Practice:
- !== to test for inequality
Why: When testing for equality or inequality, if the operands (the objects being compared) are of a different type, then == may yield incorrect results in certain instances. For example, ' ' == 0, will return true, when in fact it should be false. The === will correctly return false. Bottom line: use === and !== instead of == and !=.
Yeah, I can hear it now…"these things are so uncommon that they're not even worth talking about". But, like constructing a good building, its better to start with a strong foundation than to continue building upon minor mistakes, which over time may cause it to collapse. And furthermore, if the JavaScript guru Crockford says it’s a good idea, well, then I will faithfully follow in pursuit! Happy coding.