Javascript validation with php sample 1 - php

Question

I have a form with 4 fields
First Name (required)
Last Name (required)
Email (required)
phone (optional) (if user enter any it should validate to a number or not) below is the form i have
<form name="myForm" method="post" onsubmit="return validate();">
First Name : <input type="text" name="fname" id="id_fname"> <br>
Last Name : <input type="text" name="lname" id="id_lname"> <br>
Email : <input type="text" name="email" id="id_email"> <br>
Phone : <input type="text" name="phone" id="id_phone"> <br>
<input type="submit" value="send">
</form>
And below is the javascript code
<script type="text/javascript">
function validate()
{
if (document.myForm.id_fname.value == '') {
alert("Enter First Name");
return false;}
else if(document.myForm.id_lname.value == '') {
alert("Enter Last Name");
return false; }
// now here email validation is not working
else if(document.myForm.id_email.value == '' || document.myForm.id_email.value != ''){
var x = document.myForm.id_email.value;
var atpos=x.indexOf("#");
var dotpos=x.lastIndexOf(".");
if (atpos<1 || dotpos<atpos+2 || dotpos+2>=x.length)
alert("Not a valid e-mail address");
return false;
else
return true;
}
// this is for phone number, if this field is empty no validation, if this field not empty it should validate to contain only numbers
else if(document.myForm.id_phone != '') {
var ValidChars = "0123456789";
var IsNumber=true;
var Char;
sText = document.form1.testfield2_phone.value ;
for (i = 0; i < sText.length && IsNumber == true; i++)
{
Char = sText.charAt(i);
if (ValidChars.indexOf(Char) == -1)
{
IsNumber = false;
}
}
if(IsNumber == false)
alert("Enter valid Number");
return false;
else
return true;
}
else
return true;
document.myForm.submit();
}
</script>
Email validation and phone validation are not working when i comment these email and phone i get validation good for first name and last name... is there any error in code for validation.
And when a form is submitted, when we refresh then details are resubmitted again, how to avoid this.

Answer 1

Why do you do it so complicated???
if (document.myForm.id_fname.value.length < 3) {
alert("Enter First Name");
return false;
} else if (document.myForm.id_lname.value.length < 3) {
alert("Enter Last Name");
return false;
} else if (!/^\S+#\S+\.\w+$/.test(document.myForm.id_email.value)) {
alert("Not a valid e-mail address");
return false;
} else if (!/^\d+$/.test(document.myForm.id_phone.value)) {
alert("Enter valid Number");
return false;
}
return true;

Answer 2

There are multiple syntax errors, which are mainly related to the else if
For the resubmissions have alook at Post - Redirect - Get (PRG) is a common design pattern for web developers to help avoid certain duplicate form submissions and allow user agents to behave more intuitively with bookmarks and the refresh button.