Make input accept one letter with regex and jQuery

Question

I have this:

$('.onealphaonly').bind('keyup blur',function(){ 
    var node = $(this);
    node.val(node.val().replace(/[^a-zA-Z]/g{1},'') ); }
);

where what I hope it would do is that it allows the user to input only one letter in an input field. It accepts only letters for now, but I cannot make it to allow only one letter (and have searched dozens of SO answers). Any ideas?

Live demo

@DimitarChristoff I think this could be posted as an answer. =) — gsamaras, Aug 11 '17 at 21:32

Erazihel · Accepted Answer · 2017-08-11T21:50:08.630

1

Capture the first letter of the input and replace everything by its value.

$('.onealphaonly').bind('keyup', function() { 
    const node = $(this);
    node.val(node.val().replace(/^([a-zA-Z]).*/g, '$1'));
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input class="onealphaonly"/>

edited Aug 11 '17 at 21:50

answered Aug 11 '17 at 21:29

Erazihel

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Regex101 says: `{1} Quantifier — Matches exactly one time (meaningless quantifier)`. – gsamaras Aug 11 '17 at 21:37
1

@gsamaras You're right, the `{1}` is completely useless, sorry about that. Post edited :) – Erazihel Aug 11 '17 at 21:50
Thank you Erazihel. Do you think my question was so bad to get a downvote? – gsamaras Aug 11 '17 at 21:51

score 1 · Answer 2 · answered Aug 11 '17 at 21:31

You have a syntax error in your regex. It should be formatted as /pattern/flags. Here is a regex that works: node.val().replace(/^([a-zA-Z])[a-zA-Z]+/g, '$1'). There are many ways of crafting a regex that'll do the job, however why don't you use the following instead:

node.val().substr(0, 1);

Also, you may have better success by also checking if the length of the value is greater than one and using e.preventDefault() like so:

if (node.val().length >= 1) {
    e.preventDefault();
    return false;
}

Fiddle: http://jsfiddle.net/ka52kdLv/14/

Thanks Adam for the answer and the upvote! – gsamaras Aug 11 '17 at 21:39 — gsamaras, Aug 11 '17 at 21:39

Make input accept one letter with regex and jQuery

2 Answers2