Registration form verification js code on mobile phone

js code

<script type="text/javascript">
function checkreg() {
var myreg = /^(((13[0-9]{1})|(15[0-9]{1})|(18[0-9]{1})|(17[0-9] {1}))+\d{8})$/;
if(document.form1.name.value == "") {
//alert("Please enter your username!");
document.getElementById("tish").innerHTML = "<font color='red'>Please enter your username!</font>";
form1.name.focus();
return false;
}
document.getElementById("tish").innerHTML = "<font color='green'>Correct</font>";
// if (document.form1.User.value.length<4 || document.form1.User.value.length>15)
// {
// alert("Username length is limited to 4-15 characters!");
// form1.User.focus();
// return false;
// }
if(document.form1.password.value == "") {
//alert("Please enter password!");
document.getElementById("ts").innerHTML = "<font color='red'>Please enter the password</font>";
form1.password.focus();
return false;
}
if(document.form1.password.value.length < 6 || document.form1.password.value.length > 20) {
//alert("Password length is limited to 6-20 characters!");
document.getElementById("ts").innerHTML = "<font color='red'>Password length is limited to 6-20 characters!</font>";
form1.password.focus();
return false;
}
document.getElementById("ts").innerHTML = "<font color='green'>Correct</font>";
if(document.form1.password.value != document.form1.Pwdagain.value) {
document.getElementById("tishi").innerHTML = "<font color='red'>The two passwords are not the same</font>";
form1.password.focus();
return false;
}
document.getElementById("tishi").innerHTML = "<font color='green'>Correct</font>";
// alert("Registration successful!");
// location.href="http://www.lanrenzhijia.com";

if(!myreg.test(document.form1.phone.value)) {
document.getElementById("tss").innerHTML = "<font color='red'>wrong mobile phone number</font>";
form1.password.focus();
return false;
}
document.getElementById("tss").innerHTML = "<font color='green'>Correct</font>";
if(document.form1.code.value == "") {
			
document.getElementById("tsi").innerHTML = "<font color='red'>The verification code cannot be empty</font>";
form1.code.focus();
return false;
}
document.getElementById("tsi").innerHTML = "<font color='green'>Correct</font>";
location.href="homepage.html";
}

function sendMessage(t) {
var myreg = /^(((13[0-9]{1})|(15[0-9]{1})|(18[0-9]{1})|(17[0-9] {1}))+\d{8})$/;
if(!myreg.test(document.form1.phone.value))
{
alert('Please enter a valid mobile phone number!');
return false;
} //
document.form1.dynamic.disabled = true;
for(i = 1; i <= t; i++) {
window.setTimeout("update_p(" + i + "," + t + ")", i * 1000);
}

}

function update_p(num, t) {
if(num == t) {
document.form1.dynamic.value = "Resend";
document.form1.dynamic.disabled = false;
}
else {
printnr = t - num;
document.form1.dynamic.value = "Resend in (" + printnr + ") seconds";
}
}
</script>