Regex not working in HTML5 pattern

Question

So I have this regex intended to let pass all text but those that contain as initial chars the "34" sequence:

^(?!34)(?=([\w]+))

The regex is working fine for me in https://regex101.com/r/iN1yN3/2 , check the tests to see the intended behavior.

Any Idea why it isn't working in my form?

<form>
    <input pattern="^(?!34)(?=([\w]+))" type="text">
    
        <button type="submit">Submit!</button>
</form>

Note that your example on regex101 does not work if you change the flavour to JavaScript — James Thorpe
– James Thorpe, Commented Jun 22, 2015 at 19:24
@JamesThorpe It does work, check the matches section. Also all the test run. The problem is that it should match the whole string. — Istar_Eldritch
– Istar_Eldritch, Commented Jun 26, 2015 at 10:06

mcrumley · Accepted Answer · 2015-06-22 19:23:14Z

4

The pattern attribute has to match the entire string. Assertions check for a match, but do not count towards the total match length. Changing the second assertion to \w+ will make the pattern match the entire string.

You can also skip the implied ^, leaving you with just:

<input pattern="(?!34)\w+" type="text">

answered Jun 22, 2015 at 19:23

mcrumley

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2 Comments

Istar_Eldritch Over a year ago

Fixed and improved. This is what I was looking for.

Istar_Eldritch Over a year ago

The pattern attribute has to match the entire string. This is the golden answer. Just commenting again as I had to think on it and just realize that the answer was written as the first sentence of the response. Thanks again @mcrumley

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