Textarea with javascript validation

Question

How can I validate the following textarea using a pure Javascript not Jquery? Can anyone help me please.

<script>
function val()
{
    // 1. only allowed alphanumeric characters, dash(-), comma(,) and no space
    // 2. alert if person is trying to input not allowed chars as in 1.
} 
</script>

<form>  
    <textarea name="pt_text" rows="8" cols="8" class="input" onkeydown="return val();"></textarea>
</form>

Just a suggestion for point 2. When you say alert, please don't use an actual alert box. — Smeegs
– Smeegs, Commented Mar 26, 2014 at 14:22
onkeydown isnt really a good for validating stuffs.. what if someone copy pastes with mouse o_O — Psych Half
– Psych Half, Commented Mar 26, 2014 at 14:32

tewathia · Accepted Answer · 2014-03-26 14:39:45Z

1

Try something like:

document.querySelector('.input').onkeypress = function validate(e) {
    if (String.fromCharCode(e.keyCode).match(/[\w,-]/) == null) {
        alert('not allowed');
        e.preventDefault();
    }
};

DEMO

Edit: As pointed out by tenub, \w also allows _, so modify the regex to: /[A-Za-z0-9,-]/

DEMO

answered Mar 26, 2014 at 14:39

tewathia

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Comments

Trygve Flathen · Accepted Answer · 2014-03-26 14:33:09Z

0

This regex will match only valid strings:

/^[\w,-]*$/

Use + instead of * if you don't allow empty strings.

answered Mar 26, 2014 at 14:33

Trygve Flathen

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1 Comment

Trygve Flathen Over a year ago

Ah, right. /^[-\w,-[_]]*$/ if character class subtraction is supported, otherwise /^[a-zA-Z0-9,-]*$/. (Probably use the last one anyway for readability.)

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