Create a javascript regex to find numbers starting with a # (but not including HTML special characters or existing links)

Question

I'm trying to create links from certain strings. I've tried this:

([^&]#)([0-9]+)(?![^<>]*>)

But it's not working quite correctly.

Test 1: &#106
Test 2: #1040
Test 3: some text followed by #1060
Test 4: <a href="#1060">#1060</a>
Test 5: <b>#1078</b> (...or any other tag except <a>)

Test 1 & 4: should NOT match.
Test 2, 3 & 5: should match.

I.e. It should match for a #number in any tag except for a link tag (nor it's attributes).

Here's a jsfiddle where you can test it out: http://jsfiddle.net/xqnjs2uq/3/

The regex in question is labelled "regex3" I've included two other regex's in there because their part of the bigger picture – just to be able to check whether this regex interferes with any of those.

UPDATE With help from @chsdk I've managed to find a way to do this with two regex's (see regex3 and regex4 in the following jsfiddle)...

http://jsfiddle.net/xqnjs2uq/6/

/[^&|href="]+(#[0-9]+\b)/gim  --> matches Test 3 and 5 above
/^(#[0-9]+)/   --> required to match Test 2 above

1st prize would be for condensing this into a single regex. Is that possible?

That seems to work on regexplanet.com/advanced/javascript/index.html but fails in my real-world tests for Test 2. Weird? — geoidesic
– geoidesic, Commented Sep 3, 2015 at 8:22
It is weird, I guess you should update the question with how you perform your real-life tests. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Sep 3, 2015 at 8:25
Tx. I've updated. Test 2 is passing but actually my real world test was not an example of Test 2 but rather of the newly added Test 5. — geoidesic
– geoidesic, Commented Sep 3, 2015 at 9:12
Perhaps, (^#|[^&\n]#)([0-9]+)(?![^<>\n]*(?:<\/a>|[^>\n]*>[^<\n]*<\/a>)) then? — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Sep 3, 2015 at 9:18

cнŝdk · Accepted Answer · 2015-09-03 13:54:05Z

2

Simply use the following regex /[^&|href="](#[0-9]+)/g.

This is a live DEMO, giving those results:

With the following matches:

EDIT:

I missed the part where you want to avoid matching this expression within links, this is the regex you will need for this:

[^&|"](#[0-9]+\b)(?!<\/a>)

We added the \b here to make sure it takes the whole expression at a word boundary and (?!<\/a>) to avoid matching links.

And this is the Live DEMO again, and you can test it in the following Snippet:

var re = /[^&|"](#[0-9]+\b)(?!<\/a>)/g;
var str = 'Test 1: &#106\nTest 2: #1040\nTest 3: some text followed by #1060\nTest 4: <a href="#1060">#1060</a>\nTest 5: <b>#1078</b> (...or any other tag except <a>)';
var m;

while ((m = re.exec(str)) !== null) {
  if (m.index === re.lastIndex) {
    re.lastIndex++;
  }
  document.write("<b>" + m[1] + "</b><br/>");
}

edited Sep 3, 2015 at 13:54

answered Sep 3, 2015 at 10:40

cнŝdk

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6 Comments

geoidesic Over a year ago

This isn't working for me. It's eating closing brace of tags. E.g. <p<a href="#/app/job/1078/1" target="_blank">#1078</a></p>. Note the broken p tag. This is after using replace on <p>#1078</p> using that regex.

cнŝdk Over a year ago

This fiddle is broken, but just use the code in my snippet to replace it,

geoidesic Over a year ago

I have: jsfiddle.net/7acfut1r/1 ... but it still doesn't work. Please notice how the <p> tag has become <p (without the closing brace).

cнŝdk Over a year ago

@geoidesic Yes I see, the problem is that the regex is matching the sequence group but capturing the previous character too, so the solution is to use regex3.exec() method like this match = regex3.exec(string)[1] and then use match variable in your replace, this is the updated fiddle, I hope it helps.

geoidesic Over a year ago

Thx @chsdk. Seems to work for some strings but not others. I've updated the jsfiddle with all the tests: jsfiddle.net/xqnjs2uq/5.

|

user5125586 · Accepted Answer · 2015-09-03 10:24:24Z

1

Try (^(#|(<[b-zB-Z]+>))((0-9)+)(?!(<\/*a>*)))

answered Sep 3, 2015 at 10:24

user5125586

Comments

Neo · Accepted Answer · 2015-09-03 10:31:52Z

0

Here's my solution ^^. Hope this help you

/#[0-9]+/gi

answered Sep 3, 2015 at 10:31

Neo

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