Javascript RegEx for float between boundries

Question

I searched around and after running this through a few RegEx builders it seems to do what I want... but when I actually try and implement it it never seems to work.

This is the expression I'm using: (?<=\[)[0-9]+(?:\.[0-9]*)?(?=\])

From my understanding, this is supposed to match any numbers between the [] symbols. I am unconcerned if it is a true float, positive or negative, or any of that, because it is predetermined.

The purpose of this is that I have a set number of prebuilt <select> tags that the website has already built. I need to loop through all of the select tags and get the currently selected option, and inside of that match the number between [].

<select>
   <option>Stuff [193.33]</option>
   <option>Stuff2 [19232l.39393]</option>
</select>

Something like...

$('#content_area').$('input:select').change(function(){
   $('#content_area').$('select option:selected').each(function(){}

I am unaware as to why,

the expression gives me a syntax error even if I just return it in an alert, and
how would I construct the loop?

Did you mean to have the letter l in <option>Stuff2 [19232l.39393]</option>? I ask because your regex won't match any letters. — Cameron Skinner
– Cameron Skinner, Commented Jan 10, 2011 at 23:57

SLaks · Accepted Answer · 2011-01-10 23:34:19Z

2

Your jQuery code is completely wrong.

You're probably trying to write

$('#content_area select').change(function() {
    var value = $(this).val();
});

answered Jan 10, 2011 at 23:34

SLaks

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Phrogz · Accepted Answer · 2011-01-10 23:35:52Z

0

a) You should put this as the value of your option, e.g.

<select>
   <option value="193.33">Stuff [193.33]</option>
   <option value="19232l.39393">Stuff2 [19232l.39393]</option>
</select>

b) If you can't change your HTML, then the regex you want is:

/\[\d+(\.\d+)?\]/

You can't use what you have for several reasons, including the fact that most JS interpreters do not not support positive lookbehind assertions. Because of this, we'll have to capture the square brackets and then ignore them, like so:

$('foo option:selected').each(function(){
  var float = /\[(\d+(\.\d+)?)\]/.exec(this.value)[1] * 1;
});

answered Jan 10, 2011 at 23:35

Phrogz

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1 Comment

Phrogz Over a year ago

@AnonymousDownvoter I would appreciate it if you would explain why you felt my answer was unworthy of a '1' ranking. Drive-by downvoting can help clarify a large pool of answers, but it is much better to leave a comment telling others why you feel they should steer clear of this answer.

Cameron Skinner · Accepted Answer · 2011-01-10 23:52:40Z

0

According to this article Javascript does not support lookbehind. Would this expression work for you?

(?:\[)([0-9]+(?:\.[0-9]*)?)(?:\])

EDIT: Or, more concisely \[(\d+(?:\.\d*)?)\] (Thanks to Phrogz for pointing this out)

EDIT2: To address the jQuery bit, maybe something like this would work (lifted from the jQuery :selected documentation):

$("select").change(function () {
    $("select option:selected").each(function () {
        var value = $(this).text();
        // Do regex magic
    });
});

edited Jan 10, 2011 at 23:52

answered Jan 10, 2011 at 23:35

Cameron Skinner

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3 Comments

Phrogz Over a year ago

In a regex with non-capturing groups, (?:\\[) is the same as simply \\[. Also, you forgot to escape the literal period in the original.

Cameron Skinner Over a year ago

There is a capturing group in the middle to grab the digits. I tried replacing the (?:\\[) with \\[ but it doesn't seem to match correctly. I'm not a regex guru so it could be that I'm doing something silly. Like the literal . non-escaping :)

Cameron Skinner Over a year ago

@Phrogz: No, I stand corrected. It does work when one does it right :)

Will · Accepted Answer · 2011-01-10 23:24:15Z

-1

There is a great tool here to test your regex's

http://www.regextester.com/

answered Jan 10, 2011 at 23:24

Will

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2 Comments

Phrogz Over a year ago

This is a comment, not an answer.

treeface Over a year ago

This should really be a comment, not an answer. You're just providing a tool, not really answering his question.

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