We Keep Coding

radio checked blinks in js

I want to make a code if you put your resident registration number(7 numbers) in the text box and press the result button, automatically checks the gender according to the first number(1,3 = check male/ 2,4 = check female).
But if I press the result button, the radio check will blink once and disappear. What should I do?
<form action="#" name="idForm">
<fieldset>
<legend>gender check</legend>
<input type="text" name="idNumber" maxlength="7" id="num">
<label for="num"> : 7 numbers</label>
<button name="result">result</button>
<input type="radio" id="male" name="gender">
<label for="male">man</label>
<input type="radio" id="female" name="gender">
<label for="female">woman</label>
</fieldset>
</form>
<script>
var idNumber = document.idForm.idNumber;
var result = document.idForm.result;
var male = document.getElementById('male');
var female = document.getElementById('female');
result.onclick = function(){
var v = idNumber.value;
if(v.length == 7){
if(v.charAt(0) == 1 || v.charAt(0) == 3){
male.checked=true;
}else if(v.charAt(0) == 2 || v.charAt(0) == 4){
female.checked=true;
}else{
alert('! : 7 numbers');
}
}else{
alert('! : 7 numbers');
}
};
</script>

Data Validation with "Select" Menu

A part of the application I am creating asks the user to enter the state of their current residence, it then asks the user to enter their postcode. The program then tests to see if the postcode is valid for that State.
Eg. State entered "VIC" postcode can't be >=4000 or < 3000
Instead of either receiving the error message or not, I constantly receive the error message even when the postcode is valid
JS for my WebPage
function validate () {
var result = true
var errMsg = " "
var postcode = document.getElementById("postcode").value;
var state = document.getElementById("state").value;
var other = document.getElementById("text").value;
if (state == "VIC" || postcode >= 4000 || postcode < 3000) {
errMsg = errMsg + "You have entered an invalid postcode for your chosen state\n"
result = false;
}
else if (state == "VIC" || postcode >=9000 || postcode < 8000) {
errMsg = errMsg + "You have entered an invalid postcode for your chosen state\n"
result = false;
}
else if (state == "NSW" || postcode >=3000 || postcode < 1000) {
errMsg = errMsg + "You have entered an invalid postcode for your chosen state\n"
result = false;
}
else if (state == "QLD" || postcode <4000 || postcode >= 5000) {
errMsg = errMsg + "You have entered an invalid postcode for your chosen stae\n"
result = false;
}
else if (state == "QLD" || postcode <9000 || postcode >= 10000) {
errMsg = errMsg + "You have entered an invalid postcode for your chosen state\n"
result = false;
}
else if (state == "NT" || postcode >= 1000) {
errMsg = errMsg + "You have entered an invalid postcode for your chosen state\n"
result = false;
}
else if (state == "WA" || postcode < 6000 || postcode >= 7000) {
errMsg = errMsg + "You have entered an invalid postcode for your chosen state\n"
result = false;
}
else if (state == "SA" || postcode < 5000 || postcode >= 6000) {
errMsg = errMsg + "You have entered an invalid postcode for your chosen state\n"
result = false;
}
else if (state == "TAS" || postcode < 7000 || postcode >= 8000) {
errMsg = errMsg + "You have entered an invalid postcode for your chosen state\n"
result = false;
}
else if (state == "ACT" || postcode >= 1000) {
errMsg = errMsg + "You have entered an invalid postcode for your chosen state\n"
result = false;
}
if (document.getElementById("other").checked = true || other == "If you selected Other, enter your answer here...") {
errMsg = errMsg + "You have selected other, please enter your answer into the text box provided"
result = false;
}
if (errMsg != "") {
document.getElementById("errMessage").value = errMsg;
}
return result;
}
function init() {
if (document.getElementById("applypage")!=null) {
var regForm = document.getElementById("regform");
job_apply();
regForm.onsubmit = validate;
}
else if (document.getElementById("jobspage") !=null) {
storeJobNumber();
}
}
window.onload = init;
HTML for my webPage
<!DOCTYPE html>
<html Lang="en">
<head>
<meta charset="utf-8" />
<meta name="description" content="CWA HELP DESK" />
<meta name="keywords" content="HTML, CWA, Help, Desk" />
<meta name="author" content ="Harry Keys" />
<title>Application Form</title>
<link href="style/style.css" rel="stylesheet" type="text/css">
<script src="apply.js"></script>
</head>
<body id="applypage">
<form id="regform" method="post" action="http://mercury.swin.edu.au/it000000/formtest.php" novalidate="novalidate">
<img src="images/logo.png" alt="Company Logo" />
<h1> Job Application Form </h1>
<fieldset>
<p><label for="jobNumber">Job Reference Number</label>
<input type="text" onkeyup="this.value=this.value.replace(/[^\d]/,'')" name="jobNumber" id="jobNumber" maxlength="5" size="7" required="required" readonly/>
</p>
<p><label for="givenName">Given Name</label>
<input type="text" onkeypress="return /[a-z]/i.test(event.key)" name="givenName" id="givenName" maxlength="20" size="15" required="required"/>
<label for="familyName">Family Name</label>
<input type="text" onkeypress="return /[a-z]/i.test(event.key)" name="familyName" id="familyName" maxlength="20" size="15" required="required"/>
</p>
</fieldset>
<fieldset>
<legend>Personal Details</legend>
<p><label for="dob">Date of Birth</label>
<input type="date" name="dob" id="dob" required="required"/>
</p>
<p><label for="staddress">Street Address</label>
<input type="text" name="staddress" id="staddress" maxlength="40" required="required"/>
<label for="suburb">Suburb/Town</label>
<input type="text" name="suburb" id="suburb" maxlength="40" required="required"/>
</p>
<p><label for="state">State</label>
<select name="state" id="state">
<option value="Please Select">Please Select</option>
<option value="VIC">VIC</option>
<option value="NSW">NSW</option>
<option value="QLD">QLD</option>
<option value="NT">NT</option>
<option value="WA">WA</option>
<option value="SA">SA</option>
<option value="TAS">TAS</option>
<option value="ACT">ACT</option>
</select>
</p>
<p><label for="postcode">Postcode</label>
<input type="text" name="postcode" id="postcode" onkeyup="this.value=this.value.replace(/[^\d]/,'')" maxlength="4" size="4" required="required"/>
</p>
<p><label for="email">Email</label>
<input type="email" name="email" id="email" required="required"/>
</p>
<p><label for="phonenumber">Phone Number</label>
<input type="text" name="phonenumber" id="phonenumber" onkeyup="this.value=this.value.replace(/[^\d]/,'')" maxlength="12" size="12" required="required"/>
<fieldset>
<legend>Gender</legend>
<p> <label for="male">Male</label>
<input type="radio" id="male" name="Gender" value="male" required="required"/>
<label for="female">Female</label>
<input type="radio" id="female" name="Gender" value="female"/>
<label for="other">Other</label>
<input type="radio" id="undefined" name="Gender" value="undefined"/>
</p>
</fieldset>
<fieldset>
<legend>Skills List</legend>
<p> <label for="teamwork">Teamwork</label>
<input type="checkbox" id="teamwork" name="Skill[]" value="Teamwork" checked="checked"/>
<label for="rubyskills">Ruby Experience</label>
<input type="checkbox" id="rubyskills" name="Skill[]" value="Rubyskills"/>
<label for="efficiency">Efficiency</label>
<input type="checkbox" id="efficiency" name="Skill[]" value="Efficiency"/>
<label for="communication">Communication</label>
<input type="checkbox" id="communication" name="Skill[]" value="Communication"/>
<label for="other">Other</label>
<input type="checkbox" id="other" name="Skill[]" value="other"/>
</p>
<p> <textarea id="text" name="Skill[]" rows="5" cols="20" placeholder="If you selected Other, enter your answer here..."></textarea>
</p>
</fieldset>
</fieldset>
<p> <textarea id="errMessage" rows="3" cols="40"></textarea> </p>
<input type="submit" value="Submit"/>
<input type="reset" value="Reset Form"/>
</form>
When I select "NSW" and enter a postcode that is not >=3000 or <1000 I should not receive an error. But I still do

I think your if-else-if construct is a little bit confusing.
I'd recommend a switch-block to validate which state has been chosen and with each case check if the postcode is in the correct range.
Something like:
function validate() {
var result = true
var errMsg = " "
var postcode = document.getElementById("postcode").value;
var state = document.getElementById("state").value;
var other = document.getElementById("text").value;
switch (state) {
case "VIC":
if (postcode >= 3000 && postcode < 4000) {
result = true;
}
break;
case "NSW":
if (postcode >= 1000 && postcode < 3000) {
result = true;
}
break;
case "QLD":
if (postcode >= 4000 && postcode < 5000) {
result = true;
}
break;
}
if (!result) {
errMsg = errMsg + "You have entered an invalid postcode for your chosen state\n";
}
if (document.getElementById("other").checked = true || other == "If you selected Other, enter your answer here...") {
errMsg = "You have selected other, please enter your answer into the text box provided"
result = false;
}
if (errMsg != "") {
document.getElementById("errMessage").value = errMsg;
}
return result;
}

Action attribute not working on JS validated form

The files are in the the correct locations, both the form page and form complete page are in the same folder. When I click submit, it validates the form correctly, but if everything is entered correctly and validates, it does nothing, just takes away the asterisks like it's supposed to in the js. I want it to link to the form_complete.html page after you hit submit and the validation runs, but after it validates nothing happens,
The html:
<form id="contactform" action="form_complete.html" method="post">
<p class = "labelp">
<label for="name">Name: </label>
<input type="text" name="name" id="name" placeholder="Enter your name" >
<span>*</span><br><br>
</p>
<p class = "labelp">
<label for="age">Age: </label>
<input type="text" min="18" max="100" name="age" id="age" placeholder="Enter your age">
<!-- using type=text so I can practice isNaN in js -->
<span>*</span><br><br>
</p>
<p class = "labelp"></p>
<label for="country">Country: </label>
<select name="country" id="country">
<option value ="">Select a country</option>
<option>USA</option>
<option>Canada</option>
<option>Mexico</option>
<option>Brazil</option>
<option>Japan</option>
<option>China</option>
<option>Other</option>
</select>
<span>*</span><br><br>
</p>
<p class = "labelp">
<label for="email">E-mail: </label>
<input type="email" name="email" id="email" placeholder="Enter your E-mail">
<span>*</span><br><br>
</p>
<p class = "labelp">
<label for="bday">Birthday: </label>
<input type="date" name="bday" id="bday">
<span>*</span><br><br>
</p>
<p class = "labelp">
<label for="gender" id="gender">Gender: </label>
<input type="radio" name="gender" value="male" id="male"> Male
<input type="radio" name="gender" value="female" id="female"> Female
<input type="radio" name="gender" value="other" id="other"> Other
<br><br>
</p>
<label>Comments: </label>
<textarea rows="5" cols="30"> </textarea><br><br>
<input type="button" id="registerbtn" value="Submit">
<input type="button" id="resetbtn" value="Reset">
</form>
The javascript:
"use strict";
var $ = function(id) { return document.getElementById(id);};
var processEntries = function(){
var isValid = true;
// values
var name = $("name").value;
var age = $("age").value;
var country = $("country").value;
var email = $("email").value;
var bday = $("bday").value;
var gender = "";
if ($("male").checked){gender = "Male";}
if ($("female").checked){gender = "Female";}
if ($("other").checked){gender = "Other";}
console.log(gender); //check if gender buttons work
// name
if(name == ""){
$("name").nextElementSibling.firstChild.nodeValue = "This field is required!";
isValid = false;}
else{
$("name").nextElementSibling.firstChild.nodeValue = "";
}
// age
if(age == ""){
$("age").nextElementSibling.firstChild.nodeValue = "This field is required!";
isValid = false;
}
else if(isNaN(age)){
$("age").nextElementSibling.firstChild.nodeValue = "This field must be a number!";
isValid = false;
}
else{
$("age").nextElementSibling.firstChild.nodeValue = "";
}
//country
if(country == ""){
$("country").nextElementSibling.firstChild.nodeValue = "Please select a country!";
isValid = false;}
else{
$("country").nextElementSibling.firstChild.nodeValue = "";
}
//email
if(email == ""){
$("email").nextElementSibling.firstChild.nodeValue = "This field is required!";
isValid = false;}
else{
$("email").nextElementSibling.firstChild.nodeValue = "";
}
//birthday
if(bday == ""){
$("bday").nextElementSibling.firstChild.nodeValue = "This field is required!";
isValid = false;}
else{
$("bday").nextElementSibling.firstChild.nodeValue = "";
}
}
var resetForm = function(){
$("contactform").reset();
$("name").nextElementSibling.firstChild.nodeValue = "*";
$("age").nextElementSibling.firstChild.nodeValue = "*";
$("country").nextElementSibling.firstChild.nodeValue = "*";
$("email").nextElementSibling.firstChild.nodeValue = "*";
$("bday").nextElementSibling.firstChild.nodeValue = "*";
}
window.onload = function() {
$("registerbtn").onclick = processEntries;
$("resetbtn").onclick = resetForm;
$("name").focus();
}

Please put below condition at the end of "processEntries" function
if(isValid){
$("#contactform").submit();
}

Displaying error message and pre-filling a form

On the 82 line of my JavaScript I have "document.getElementById("errors").innerHTML = errMsg;" this code and I was wondering how to implement it into my HTML page so when the validation isn't correct the error message will be displayed in the correct place such as when someone is younger then 15 the error message will be displayed next to date of birth. At the moment I have my errors appearing in an alert but I'd like them to appear on the web page. I also when to know if my "storeForm" and "prefillForm" functions are correct because I tried to test them and it doesn't seem to work. How do I go about fixing these?
"use strict";
/*get variables from form and check rules*/
function validate() {
var errMsg = ""; /* stores the error message */
var result = true; /* assumes no errors */
//var JobID = document.getElementById("JobID").value;
var firstName = document.getElementById("firstName").value;
var familyName = document.getElementById("familyName").value;
var midName = document.getElementById("midName").value;
var male = document.getElementById("male").checked;
var female = document.getElementById("female").checked;
var street = document.getElementById("street").value;
var suburb = document.getElementById("suburb").value;
var state = document.getElementById("state").options[document.getElementById("state").selectedIndex].text;
var postcode = document.getElementById("postcode").value;
var email = document.getElementById("email").value;
var number = document.getElementById("number").value;
var XML = document.getElementById("XML").checked;
var Java = document.getElementById("Java").checked;
var Python = document.getElementById("Python").checked;
var SQL = document.getElementById("SQL").checked;
var PERL = document.getElementById("PERL").checked;
var MySQL = document.getElementById("MySQL").checked;
var Windows = document.getElementById("Windows").checked;
var UNIX = document.getElementById("UNIX").checked;
var Linux = document.getElementById("Linux").checked;
var other = document.getElementById("other").checked;
var otherText = document.getElementById("otherText").value;
var dob = document.getElementById("dob").value.split("/");
var date = new Date(dob[2], parseInt(dob[1]) - 1, dob[0]);
var today = new Date();
var age = today.getFullYear() - date.getFullYear();
//get varibles from form and check rules here
// if something is wrong set result = false, and concatenate error message
if (age >= 80) { // Outside age ranges.
errMsg = errMsg + "You must be 80 or younger to apply for this job\n";
result = false;
}
if (age <= 15) { // Outside age ranges.
errMsg = errMsg + "You must be 15 or older to apply for this job\n";
result = false;
}
if (!(postcode.charAt(0) == 3 || postcode.charAt(0) == 8) && state == "VIC") {
errMsg = errMsg + "Your state and postcode do not match. State VIC postcodes must start with a 3 or 8\n";
result = false;
} else if (!(postcode.charAt(0) == 1 || postcode.charAt(0) == 2) && state == "NSW") {
errMsg = errMsg + "Your state and postcode do not match. State NSW postcodes must start with a 1 or 2\n";
result = false;
} else if (!(postcode.charAt(0) == 4 || postcode.charAt(0) == 9) && state == "QLD") {
errMsg = errMsg + "Your state and postcode do not match. State QLD postcodes must start with a 4 or 9\n";
result = false;
} else if (!(postcode.charAt(0) == 0) && state == "NT") {
errMsg = errMsg + "Your state and postcode do not match. State NT postcodes must start with a 0\n";
result = false;
} else if (!(postcode.charAt(0) == 6) && state == "WA") {
errMsg = errMsg + "Your state and postcode do not match. State WA postcodes must start with a 6\n";
result = false;
} else if (!(postcode.charAt(0) == 5) && state == "SA") {
errMsg = errMsg + "Your state and postcode do not match. State SA postcodes must start with a 5\n";
result = false;
} else if (!(postcode.charAt(0) == 7) && state == "TAS") {
errMsg = errMsg + "Your state and postcode do not match. State TAS postcodes must start with a 7\n";
result = false;
} else if (!(postcode.charAt(0) == 0) && state == "ACT") {
errMsg = errMsg + "Your state and postcode do not match. State ACT postcodes must start with a 0\n";
result = false;
} else {
result = true;
}
if (other && document.getElementById("otherText").value.trim().length === 0) {
errMsg = errMsg + "You have selected other skills, you must enter one other skill in the text box\n";
result = false;
}
if (errMsg != "") { //only display message box if there is something to show
alert(errMsg);
//document.getElementById("errors").innerHTML = errMsg;
}
if (result == true) {
storeForm(firstName, familyName, midName, dob, male, female, street, suburb, state, postcode, email, number, XML, Java, Python, SQL, PERL, MySQL, Windows, UNIX, Linux, other, otherText)
}
return result; //if false the information will not be sent to the server
}
function storeForm(firstName, familyName, midName, dob, male, female, street, suburb, state, postcode, email, number, XML, Java, Python, SQL, PERL, MySQL, Windows, UNIX, Linux, other, otherText) {
//get values and assign them to sessionStorage attribute.
//we use the same name for the attrubute and the element id to avoid confustion
sessionStorage.firstName = firstName;
sessionStorage.familyName = familyName;
sessionStorage.midName = midName;
sessionStorage.dob = dob;
sessionStorage.male = male;
sessionStorage.female = female;
sessionStorage.street = street;
sessionStorage.suburb = suburb;
sessionStorage.state = state;
sessionStorage.postcode = postcode;
sessionStorage.email = email;
sessionStorage.number = number;
sessionStorage.XML = XML;
sessionStorage.Java = Java;
sessionStorage.Python = Python;
sessionStorage.SQL = SQL;
sessionStorage.PERL = PERL;
sessionStorage.MySQL = MySQL;
sessionStorage.Windows = Windows;
sessionStorage.UNIX = UNIX;
sessionStorage.Linux = Linux;
sessionStorage.other = other;
sessionStorage.otherText = otherText;
}
/* check if session day on user exists and if so prefill the form*/
function prefillForm() {
if (sessionStorage.firstName != undefined) {
document.getElementById("firstName").value = sessionStorage.firstName;
document.getElementById("familyName").value = sessionStorage.familyName;
document.getElementById("midName").value = sessionStorage.midName;
document.getElementById("dob").value = sessionStorage.dob;
if (sessionStorage.male == ("true")) {
document.getElementById("male").checked = true;
}
if (sessionStorage.female == ("true")) {
document.getElementById("female").checked = true;
}
document.getElementById("street").value = sessionStorage.street;
document.getElementById("suburb").value = sessionStorage.suburb;
document.getElementById("state").value = sessionStorage.state;
document.getElementById("postcode").value = sessionStorage.postcode;
document.getElementById("email").value = sessionStorage.email;
document.getElementById("number").value = sessionStorage.number;
if (sessionStorage.XML == ("true")) {
document.getElementById("XML").checked = true;
}
if (sessionStorage.Java == ("true")) {
document.getElementById("Java").checked = true;
}
if (sessionStorage.Python == ("true")) {
document.getElementById("Python").checked = true;
}
if (sessionStorage.SQL == ("true")) {
document.getElementById("SQL").checked = true;
}
if (sessionStorage.PERL == ("true")) {
document.getElementById("PERL").checked = true;
}
if (sessionStorage.MySQL == ("true")) {
document.getElementById("MySQL").checked = true;
}
if (sessionStorage.Windows == ("true")) {
document.getElementById("Windows").checked = true;
}
if (sessionStorage.UNIX == ("true")) {
document.getElementById("UNIX").checked = true;
}
if (sessionStorage.Linux == ("true")) {
document.getElementById("Linux").checked = true;
}
if (sessionStorage.other == ("true")) {
document.getElementById("other").checked = sessionStorage.other;
}
document.getElementById("otherText").value = sessionStorage.otherText;
}
}
function referenceNum1() {
//this function defines the local storage for the first job
localStorage.JobID = "QM593";
}
function referenceNum2() {
//this function defines the local storage for the second job;
localStorage.JobID = "CS197";
}
function init() {
var path = window.location.pathname;
var page = path.split("/").pop();
if (page == "apply.html") {
var regForm = document.getElementById("regform"); // get ref to the HTML element
window.onload = prefillForm();
regForm.onsubmit = validate; //register the event listener
//this puts the job id into the field
document.getElementById("JobID").value = localStorage.JobID;
} else {
//this makes it so that the 2 different functions run when the hyperlinks are clicked
var job1 = document.getElementById("job1");
var job2 = document.getElementById("job2");
var JobID
job1.onclick = referenceNum1;
job2.onclick = referenceNum2;
}
}
window.onload = init;
<article>
<header>
<h1>The Virtual World</h1>
<nav>
<p class="menu">Home</p>
<p class="menu">Jobs</p>
<p class="menu">Apply</p>
<p class="menu">About</p>
<p class="menu">Enhancements</p>
</nav>
</header>
<section id="required">
<h5>All fields with * are required</h5>
</section>
<form id="regform" method="post" action="http://mercury.swin.edu.au/it000000/formtest.php">
<fieldset>
<legend>Job Application</legend>
<p><label for="JobID">*Job ID:</label>
<input type="text" name="JobID" id="JobID" maxlength="5" size="10" pattern="^[a-zA-Z]{2}[0-9]{3}$" required="required" /></p>
<section id="choose">
<h5>Please choose from QM593 or CS197</h5>
</section>
<fieldset>
<legend>Personal Details</legend>
<p><label for="title">*Title:</label>
<select name="title" id="title" required="required">
<option value="">Please Select</option>
<option value="title">Dr</option>
<option value="title">Mr</option>
<option value="title">Miss</option>
<option value="title">Mrs</option>
<option value="title">Ms</option>
</select></p>
<p><label for="firstName">*First Name:</label>
<input type="text" name="firstName" id="firstName" maxlength="20" size="20" pattern="^[a-zA-Z ]+$" required="required" />
<label for="familyName">*Family Name:</label>
<input type="text" name="familyName" id="familyName" maxlength="20" size="20" pattern="^[a-zA-Z ]+$" required="required" /></p>
<p><label for="midName">Middle Name:</label>
<input type="text" name="midName" id="midName" maxlength="20" size="20" pattern="^[a-zA-Z ]+$" /></p>
<p><label for="dob">*Date of Birth:</label>
<input type="text" name="dob" id="dob" placeholder="dd/mm/yyyy" pattern="\d{1,2}/\d{1,2}/\d{4}" maxlength="10" size="10" required="required" /></p>
<p>*Gender:
<label for="male">Male</label>
<input type="radio" id="male" name="sex" value="male" required="required" />
<label for="female">Female</label>
<input type="radio" id="female" name="sex" value="female" required="required" /></p>
<p><label for="street">*Street Address:</label>
<input type="text" name="street" id="street" maxlength="40" size="30" required="required" /></p>
<p><label for="suburb">*Suburb/town:</label>
<input type="text" name="suburb" id="suburb" maxlength="40" size="20" required="required" /></p>
<p><label for="state">*State:</label>
<select name="state" id="state" required="required">
<option value="">Please Select</option>
<option value="state">VIC</option>
<option value="state">NSW</option>
<option value="state">QLD</option>
<option value="state">NT</option>
<option value="state">WA</option>
<option value="state">SA</option>
<option value="state">TAS</option>
<option value="state">ACT</option>
</select></p>
<p><label for="postcode">*Postcode:</label>
<input type="text" name="postcode" id="postcode" minlength="4" maxlength="4" size="10" pattern="^[0-9]{4}$" required="required" /></p>
<p><label for="email">*Email:</label>
<input type="email" name="email" id="email" size="30" required="required" /></p>
<p><label for="number">*Phone number:</label>
<input type="tel" name="number" id="number" minlength="8" maxlength="12" size="10" required="required" /></p>
<p>Skill list:</p>
<p><label for="C/C+">C/C+</label>
<input type="checkbox" id="C/C+" name="category[]" checked="checked" /></p>
<p><label for="XML">XML</label>
<input type="checkbox" id="XML" name="category[]" /></p>
<p><label for="Java">Java</label>
<input type="checkbox" id="Java" name="category[]" /></p>
<p><label for="Python">Python</label>
<input type="checkbox" id="Python" name="category[]" /></p>
<p><label for="SQL">SQL</label>
<input type="checkbox" id="SQL" name="category[]" /></p>
<p><label for="PERL">PERL</label>
<input type="checkbox" id="PERL" name="category[]" /></p>
<p><label for="MySQL">MySQL</label>
<input type="checkbox" id="MySQL" name="category[]" /></p>
<p><label for="Windows">Windows</label>
<input type="checkbox" id="Windows" name="category[]" /></p>
<p><label for="UNIX">UNIX</label>
<input type="checkbox" id="UNIX" name="category[]" /></p>
<p><label for="Linux">Linux</label>
<input type="checkbox" id="Linux" name="category[]" /></p>
<p><label for="other">Other Skills:</label>
<input type="checkbox" id="other" name="category[]" /></p>
<textarea id="otherText" name="other" rows="8" cols="70" placeholder="Please write any other skills you may have here..."></textarea>
</p>
</fieldset>
</fieldset>
<input type="submit" value="Apply" />
<input type="reset" value="Reset Application" />
</form>
</article>

you may create a generic function like that :
function show_error(element, message) {
element.parentElement.innerHTML += "<span class='error'>" + message + "</span>";
}
//call the function
show_error(document.getElementById('street'), 'error message');
.error {
color: red;
}
<p><label for="street">*Street Address:</label>
<input type="text" name="street" id="street" maxlength="40" size="30" required="required" /></p>
<p><label for="suburb">*Suburb/town:</label>
<input type="text" name="suburb" id="suburb" maxlength="40" size="20" required="required" /></p>
Then you can add another function to remove this error.

You can do the below to update when there is an error. I have added a small code to demonstrate.
$(document).ready(function() {
$("#btn").click(function() {
validate();
});
});
function validate() {
var errMsg = "";
var date = new Date($('#dpDoB').val());
var today = new Date();
var age = today.getFullYear() - date.getFullYear();
if (age >= 80) { // Outside age ranges.
errMsg = errMsg + "You must be 80 or younger to apply for this job\n";
$("#dob").append("<span>" + errMsg + "</span>");
result = false;
}
if (age <= 15) { // Outside age ranges.
errMsg = errMsg + "You must be 15 or older to apply for this job\n";
$("#dob").append("<span>" + errMsg + "</span>");
result = false;
}
}
<script src="https://code.jquery.com/jquery-3.2.1.min.js" integrity="sha256-hwg4gsxgFZhOsEEamdOYGBf13FyQuiTwlAQgxVSNgt4=" crossorigin="anonymous"></script>
<div id="form">
<div id="dob">
<input id="dpDoB" type="date" />
</div>
<div>
<input type="button" id="btn" class="btn btn-default" value="click me">
</div>
</div>

Making JS Alert Look More Professional

Can someone help me make this alert look much nicer? Like Maybe split up Each text box on its own line? I can not figure out how to make this look a lot cleaner and not just all piled on one line.
To see alert hit Lien radio button and then hit next without filling textboxes
http://jsfiddle.net/t4Lgm0n2/9/
function validateForm(){
var QnoText = ['lien']; // add IDs here for questions with optional text input
var ids = '';
flag = true;
for (i=0; i<QnoText.length; i++) {
CkStatus = document.getElementById(QnoText[i]).checked;
ids = QnoText[i]+'lname';
var eD = "";
if (CkStatus && document.getElementById(ids).value == '') {
eD = eD+' lienholder name';
document.getElementById(ids).focus();
flag = false;
}
ids2 = QnoText[i]+'laddress';
if (CkStatus && document.getElementById(ids2).value == '') {
eD=eD+' lienholder address';
document.getElementById(ids2).focus();
flag = false;
}
ids3 = 'datepicker2';
if (CkStatus && document.getElementById(ids3).value == '') {
eD=eD+' lien date';
document.getElementById(ids3).focus();
flag = false;
}
if(eD!="") alert("Please enter "+eD);
}
return flag;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.0/jquery.min.js"></script>
<input type="radio" value="Yes" name="lien" id="lien" required="yes" onchange="showhideForm(this.value);"/><label for="lien">Lien</label>
<input type="radio" value="None" name="lien" id="nolien" onchange="showhideForm(this.value);"/><label for="nolien">No Lien</label>
<script type="text/javascript">
function showhideForm(lien) {
if (lien == "Yes") {
document.getElementById("div1").style.display = 'block';
document.getElementById("div2").style.display = 'none';
}
else if (lien == "None") {
document.getElementById("div2").style.display = 'block';
document.getElementById("div1").style.display = 'none';
$("#div1 > .clearfix input:text").val("");
}
}
</script>
<div id="div1" style="display:none">
<div class="clearfix">
<label for="lname">Lienholder Name:</label>
<input type="text" name="lienlname" validateat="onSubmit" validate="maxlength" id="lienlname" size="54" maxlength="120" message="Please enter lienholder name." value="">
</p>
<p>
<label for="laddress">Lienholder Address:</label>
<input type="text" name="lienladdress" validateat="onSubmit" validate="maxlength" id="lienladdress" size="54" maxlength="120" message="Please enter lienholder address." value="">
</p>
<p>
<label for="ldate">Date of Lien:</label>
<input type="text" name="lienldate" id="datepicker2" mask="99/99/9999" value="">
</div>
</div>
<div id="div2" style="display:none">
<!---You are not qualified to see this form.--->
</div>
<input type="submit" name="submit" value="Next" onclick="validateForm()">

You can use new line characters \n to make text more readable:
var eD = [];
if (CkStatus && document.getElementById(ids).value == '') {
eD.push('Please enter lienholder name');
document.getElementById(ids).focus();
flag = false;
}
// ...
if (eD.length) alert(eD.join('\n'));
As you can see I'm also pushing error messages into ed array, which makes it more convenient to concatenate resulting message using .join() method.
Demo: http://jsfiddle.net/t4Lgm0n2/11/