My Validation Form is not getting implement

Sir mere phone number par validation apply nahi ho raha hai please check

                   Javascript  File

function validateForm() {
let fname = document.myform.fname.value;
let lname = document.myform.lastname.value;
let pass = document.myform.password.value;
let cpass = document.myform.cpassword.value;
let mobile = document.myform.mobile.value;
let email = document.myform.email.value;

//-----------------------------------------------first Name--------------------------//

if (fname == null || fname == “”) {
document.getElementById(“first-error”)
.innerHTML = “*Please enter name”
return false
//-----------------------------------------------Last first Name--------------------------//

}if (lname == null || lname == “”) {
document.getElementById(“secod-error”).innerHTML = “*Enter last name”
return false

//----------------------------------------------password--------------------------//

}if (pass.length < 6) {
document.getElementById(“third-error”).innerHTML = “*Enter 6 digit password”
return false

//----------------------------------------------confirm Password--------------------------//

}if (pass == cpass) {
return true
}if (cpass == “”) {
document.getElementById(“four-error”)
.innerHTML = “*Enter confirm password”
return false
}if (cpass){
document.getElementById(“four-error”)
.innerHTML = “*Password not Match”
return false

//----------------------------------------------phone number--------------------------//

}if (mobile == “”) {
document.getElementById(“five-error”)
.innerHTML = “Enter mobile Number”
return false
}
}

                   HTML File


<form action="" method="post" name="myform" onsubmit="return validateForm()">

	<input class="first-forms" type="text" name="fname" placeholder="First Name">
	<span id="first-error"></span>

	<input class="first-form" type="text" name="lastname" placeholder="Last Name">
	<span id="secod-error"></span><br><br>

	<input class="second-form" type="password" name="password" placeholder="Password">
	<span id="third-error"></span><br><br>

	<input class="second-form" type="password" name="cpassword" placeholder="Confirm Password"><span id="four-error"></span><br><br>

	<input class="second-form" type="number" name="mobile" placeholder="phone Number">
	<span id="five-error"></span><br><br>

	<input class="second-form" type="email" name="email" placeholder="Email">
	<span id="six-error"></span><br><br>

	<input class="terms" type="checkbox" name="checkbox">
	<span class="term">I agreen to the <a href="#">terms</a> </span>
	
	<input id="button" type="submit" name="submit">
</form>![Screenshot (3)|690x388](upload://dJSWqerEve5z4oeBwET1JgwrNXm.png)