JavaScript/ Alphanumeric validation not working

Question

I have this reg ex for alphanumeric validation that I got from this post but it is not working with this function (I have a similar function for email and it works)

 function checkName(field) {

        var x = document.getElementById(field).value;
        var y = /^[a-z0-9]+$/i;
        //var z = /^[0-9]*$/;

        if (x == "" || !x.match(y) ) {
            alert("Invalid character");

            if (x.length <= 2 || x.length >= 15) {
                alert("Insert a name between 3 and 15 characters");
            }

            return false;
        }

    }

If I write some string/name I get both alerts. Can someone tell me what is wrong with this function?

What happens if you put just `X` in the field? Compare that to what you expect to happen and you might hit upon what you did wrong. — Niet the Dark Absol, May 09 '17 at 12:22

score 2 · Accepted Answer · answered May 09 '17 at 12:24

2

Below is the approach for alphanumeric validation:

 function checkName(field)
 {
       var x = document.getElementById(field).value;
       if (x.length <= 2 || x.length >= 15)
       {
           alert("Insert a name between 3 and 15 characters");
           return false;
       }
        var y = /^[0-9a-zA-Z]+$/;
        if (x == "" || !x.match(y) )
        {
           alert("Invalid character");
           return false;
        }
        
        alert("ALL OK");
        return true;
 }

<input type="text" id="textName" />
<button onClick="checkName('textName');">Check</button>

The Regex check for capital and small alphabets and numbers, and also checks for the length.

answered May 09 '17 at 12:24

Shakti Phartiyal

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what happens if my Name is 'Cäsar' and not 'Nero';-) – Frank Wisniewski May 09 '17 at 12:37
@FrankWisniewski That is not the OP question. If you need reference on this topic please visit http://stackoverflow.com/questions/6381752/validating-users-utf-8-name-in-javascript – Shakti Phartiyal May 09 '17 at 12:39
i don´t need an reference for this topic. The alert is *Insert a **name** between 3 and 15 characters* ... – Frank Wisniewski May 09 '17 at 12:45

score 1 · Answer 2 · answered May 09 '17 at 12:27

Your code works for me

 function checkName(field) {
        console.log(field);
        var x = field;
        var y = /^[a-z0-9]+$/i;
        if (x == "" || !x.match(y) ) {
            console.log("Invalid character");
        }
        if (x.length <= 2 || x.length >= 15) {
            console.log("Insert a name between 3 and 15 characters");
        }
    }
//valid
checkName('testdskfjskdlf');
//invalid
checkName('slkjf*%');
//too long
checkName('jjjjjjjjjjjjjjjjjjjjjjjjjjj');

JavaScript/ Alphanumeric validation not working

2 Answers2