Question

Just starting with js, decided to convert Friendfeed to a fluid app, and as part of that I need to be able to parse some numbers out of a string.

How do I complete this function?

function numMessages(text) {

    MAGIC HAPPENS (POSSIBLY THE DARK ART OF THE REGEX)

    return number;
}

input would be “Direct Messages (15)”

output would be 15.

Instincts tell me to find the first bracket then find the last bracket, and get the text in between but I don’t know how to do that. Second instinct tells me to regex for [0-9], but I don’t know how to run regexes in js. Jquery is avaliable already if needed.

Thanks!

Answer 1

This should do it:

>>> 'Direct Messages (15)'.match(/[0-9]+/g);
["15"]

Just be careful if you expect more than 1 number to be in the string:

>>> 'Direct 19 Messages (15)'.match(/[0-9]+/g);
["19", "15"]

If you only wanted the first match, you could remove the g flag:

>>> 'Direct 19 Messages (15)'.match(/[0-9]+/);
["19"]

If you only wanted to match what’s between the parentheses

>>> 'Direct 19 Messages (15)'.match(/\((.*?)\)/);
["(15)","15"] 
// first index will always be entire match, 2nd index will be captured match

As pointed out in the comments, to get the last match:

>>> var matches = 'Direct 19 Messages (15)'.match(/[0-9]+/g);
>>> matches[matches.length-1];
"15"

Though some boundary checking would also be appropriate. 🙂