Form Validation JavaScript number always return false

Question

my textbox ALWAYS returns with field is not a number, even if it is.

HTML

<form name = garysForm>
Number of adults: <input type="number" size="6" id="ofAdults" name="adultBox" min="0" max="50" required><br>
Number of children: <input type="number" size="6" id="ofChild" min="0" max="50" required><br>
Date:<input type="text" name="date" id="datepicker" required><br>   
<Button type="button"   onclick="BookingFare(); return false;">Calculate</button><br>
</form>

Javascript

var field = document.forms["garysForm"]["adultBox"].value;

    if (isNaN(field.value)) {
            alert('Please enter a valid number');

        }

You're not selecting anything, the name is invalid as it's not quoted, and using document.forms is a really poor way to get an element that has an ID — adeneo
– adeneo, Commented Mar 18, 2015 at 23:40
Also, you're calling value TWICE, which is the real problem — adeneo
– adeneo, Commented Mar 18, 2015 at 23:42
and i honestly don't care if calling document.forms is a really poor way, that is not causing a problem.... Maybe you shouldn't be so condescending if you don't even give the correct solution ? — alex23
– alex23, Commented Mar 18, 2015 at 23:55

bvaughn · Accepted Answer · 2015-03-18 23:42:41Z

1

You're calling field.value when you've assigned value to field.

var field = document.forms["garysForm"]["adultBox"].value;

if (isNaN(field.value)) {

Try this instead:

var field = document.forms["garysForm"]["adultBox"];

if (isNaN(field.value)) {

answered Mar 18, 2015 at 23:42

bvaughn

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2 Comments

alex23 Over a year ago

tried that it just breaks it so that it doesn't even relay a message back

bvaughn Over a year ago

Point me at a plunker

Anthony Rodriguez · Accepted Answer · 2015-03-19 00:35:02Z

0

I solved it by using the .elements method.

var field = document.forms["garysForm"].elements["adultBox"].value;

Then, you need to consider that an SPACE is also considered a number reference. So I applied the following logic.

var field = document.forms["garysForm"].elements["adultBox"].value;
console.log(field)
if (field=='') {
    alert('Please enter a valid number');
}
else if (isNaN(field)) {
   alert('Please enter a valid number');
}
else {
   alert(field)
}

DEMO

*Jquery is only used for demo purpose.

I hope you find this answer helpful. Thanks.

answered Mar 19, 2015 at 0:35

Anthony Rodriguez

493 bronze badges

Comments

papantonis · Accepted Answer · 2015-03-19 00:00:55Z

0

You can get the value of the adult box using its id:

var field = document.getElementById("ofAdults").value;

if (isNaN(field)) {
    ....

answered Mar 19, 2015 at 0:00

papantonis

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