how to validate a form

[Techy]

I have two fields in my form so called : invoice and cash


Now I want to validate this form on the client side with the help of
javascript in such a way that if one of these fields is empy an alert
box should pop up notifying the client.

Now if one is empty it should let the form to process

thanks

 

[Lasse Reichstein Nielsen]

I have two fields in my form so called : invoice and cash

Now I want to validate this form on the client side with the help of
javascript in such a way that if one of these fields is empy an alert
box should pop up notifying the client.

if one is empty: alert.

Now if one is empty it should let the form to process

if one is empty: continuer.

Since I don't know exactly what you want, I'll give some code
that is easily changed:

To validate a function, always use this way to call the validation function:
---
<form ... onsubmit="return validate(this)">
---
The function itself is then:
---
function validate(form) {
var cashEmpty = form.elements['cash'].value == "";
var invoiceEmpty = form.elements['invoice'].value == "";
if (cashEmpty && invoiceEmpty) {
alert("Fill in at least one of the fields: Cash or Invoice.");
return false;
}
return true;
}