Regular Expressions in CoffeeScript are Awesome
08 Feb 2012Letβs face it, regular expressions arenβt for everyone. It takes a special breed of developer to actually enjoy writing regular expressions. Although I enjoy them, the developer that comes after me may find that they are cryptic and hard to read. And yes, sometimes it takes me a little bit to decipher through an old regular expression that I wrote a while ago.
Take for example, the following regular expression. Can you tell what it is doing? If so⦠then great, but what about the developers you work with?
| var emailPattern = /^([\w.-]+)@([\w.-]+)\.([a-zA-Z.]{2,6})$/i; | |
| if ( "john.smith@gmail.com".match( emailPattern ) ) { | |
| console.log( "E-mail is valid" ); | |
| } else { | |
| console.log( "E-mail is invalid" ); | |
| } |
One of the very cool things I like about CoffeeScript is that you can annotate your regular expressions! The following snippet of CoffeeScript compiles down to the equivalent JavaScript as seen in the above code sample. Yay ;)
| emailPattern = /// ^ #begin of line | |
| ([\w.-]+) #one or more letters, numbers, _ . or - | |
| @ #followed by an @ sign | |
| ([\w.-]+) #then one or more letters, numbers, _ . or - | |
| \. #followed by a period | |
| ([a-zA-Z.]{2,6}) #followed by 2 to 6 letters or periods | |
| $ ///i #end of line and ignore case | |
| if "john.smith@gmail.com".match emailPattern | |
| console.log "E-mail is valid" | |
| else | |
| console.log "E-mail is invalid" |
Which code sample would you rather maintain? And more importantly which one would your co-worker be more likely to understand?
NOTE: The above email regular expression is very naive in it's logic. I based the above snippet from a Nettuts+ post entitled, 8 Regular Expressions You Should Know. There are much more comprehensive email regular expressions available on the internet, but I used the above one to show the value of annotation.
As a side note, some tools that I find helpful are Grant Skinnerβs Online RegExr Tool and I sometimes get inspiration for regular expressions at RegExLib.com. What tools or resources do you use for regular expressions?
