Verify if string matches regex expression

Question

I am trying this code, but I don't know why it isn't working:

<script> 
    var inputtxt = '515';
    var letters = /^[0-9]+$/;  


    if(inputtxt.value.match(letters)) {
        document.write('Your registration number have accepted : you can try another');  
        return true;  
    } else {  
        document.write('Please input alphanumeric characters only');  
        return false;  
    }  
</script>

I want to input a value (inputtxt) and then find if it contains only digits.

What am I doing wrong?

It's more semantic to use *test* rather than *match*: `if (letters.test(inputtxt))`. And you're testing only for digits, so naming the regular expression *letters* is a bit misleading. ;-) — RobG, Jun 30 '17 at 22:13
And saying "input **alphanumeric** characters only" is also quite misleading. :-) — user94559, Jun 30 '17 at 22:14
@RobG I don't see how it's any less semantic, and it reads more naturally: if this matches that ¯\_(ツ)_/¯ — Dave Newton, Jul 01 '17 at 00:52

score 0 · Answer 1 · answered Jul 01 '17 at 00:49

I don't know why the existing answers are getting down voted, but they are correct. If you were to use console.log(inputtxt.value) it would print undefined. You need to simply remove that from your if-else:

if(inputtxt.match(letters))
    {
        document.write('Your registration number have accepted : you can try another');
    }
    else
    {
        document.write('Please input alphanumeric characters only');
    }

score -1 · Answer 2 · answered Jun 30 '17 at 22:16

Remove .value to inputtxt and return true & false from javascirpt

<script>

    var inputtxt = '515';
    var letters = /^[0-9]+$/;


    if(inputtxt.match(letters))
    {
        document.write('Your registration number have accepted : you can try another');
    }
    else
    {
        document.write('Please input alphanumeric characters only');
    }
</script>

Verify if string matches regex expression

2 Answers2