How to Validate Input in JavaScript?

Question

I am trying to validate a input field. The input field should take only numbers, if not it will alert "input must be a number". And if the field is empty it will do nothing. But when I left the field empty it will aslo alert me. How can I fix this. Here is my code

<div class="form-group">
<label class="col-lg-2 control-label">Gross Salary</label>
<div class="col-lg-8">
<input class="form-control" placeholder="Gross Salary" type="text"      name="gross_salary"id="tax4">
</div>
</div>

and javascript code

<script type="text/javascript">
    var validate_int_taxid = function() {
    var tax = document.getElementById("tax4");
    var tax_id = parseFloat(tax.value);
    if (isNaN(tax_id)) {
        alert("Gross Salary  must be a Number");
        return false;
    }
    return true;
}
</script>

Thank You

I'm not sure about this but probably isNaN() probably checks for empty and null values aswell — gbestard
– gbestard, Commented Apr 8, 2014 at 7:20
Thanks guys. I solve it by myself <script type="text/javascript"> var validate_int_taxid = function() { var tax = document.getElementById("tax4"); if(tax.value.length == 0) return true; var tax_id = parseFloat(tax.value); if (isNaN(tax_id)) { alert("Gross Salary must be a Number"); return false; } return true; } </script> — Nadim Iqbal
– Nadim Iqbal, Commented Apr 8, 2014 at 7:55

Mithun Satheesh · Accepted Answer · 2014-04-08 07:27:28Z

2

make it like

var tax = document.getElementById("tax4");

if(tax.value!="") {
    var tax_id = parseFloat(tax.value);
    if (isNaN(tax_id)) {
       alert("Gross Salary  must be a Number");
       return false;
    }
    return true;
} else {

    return false;
    //do nothing

}

Here is a fiddle.

answered Apr 8, 2014 at 7:27

Mithun Satheesh

27.9k14 gold badges80 silver badges103 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Tamura · Accepted Answer · 2014-04-08 07:41:13Z

0

Here you go:

<script type="text/javascript">
var validate_int_taxid = function() {
    if (tax.value !="") {
        var tax_id = parseFloat(tax.value);
        if (isNaN(tax_id)) {
            alert("Gross Salary  must be a Number");
            return false;
        }
        return true;
    } 
    return false;
}
</script>

answered Apr 8, 2014 at 7:41

Tamura

1,7981 gold badge14 silver badges10 bronze badges

Comments

Jenz · Accepted Answer · 2014-04-08 07:42:05Z

0

Try with this.

<script type="text/javascript">
    var validate_int_taxid = function() {
    var tax = document.getElementById("tax4");
    if(tax.value!="" )
    {
    var tax_id = parseFloat(tax.value);

    if (isNaN(tax_id)) {
        alert("Gross Salary  must be a Number");
        return false;
    }
    }
}
</script>

edited Apr 8, 2014 at 7:42

answered Apr 8, 2014 at 7:20

Jenz

8,3718 gold badges50 silver badges83 bronze badges

1 Comment

Jenz Over a year ago

@Girish..that was the right way..It will return true if it is not a number..Then why u downvote for it. I am not getting !!..

Collectives™ on Stack Overflow

How to Validate Input in JavaScript?

3 Answers 3

Comments

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related