Develop Reference

Can't get my simple JavaScript Event Handler working

I am trying to get an event handler on an HTML form. I am just trying t get the simplest thing working, but I just cannot see what I am missing.
It is part of a wider project, but since I cannot get this bit working I have reduced it down the most very basic elements 1 text field and a button to try and see what it is I am missing.
All I want to do is get some text entered and flash up message in a different area on the screen.
The user enters text into the input field (id=owner).
The plan is that when the button (id="entry") is pressed the event handler (function "entry") in the entry.js file should cause a message to display.
I don't want the form to take me to a different place it needs to stay where it is
I just want some form of text to go in the: <div id="feedback" section.
When I can get it working: I intend the create the text from the various text fields that get entered.
I Know that this is beginner stuff & I know that I have reduced this down such that it barely worth thought but I would welcome any input please & thank you.
HTML code is:
<form method="post" action="">
<label for="owner">Input Owner: </label>
<input type="text" id="owner" />
<div id="feedback"></div>
<input type="submit" value="enter" id="entry" />
</form>
<script src="entry.js"></script>
Code for entry.js is:
function entry() {
var elOwner = document.getElementById('owner');
var elMsg = document.getElementByID('feedback');
elMsg.textContent = 'hello';
}
var elEntry = document.getElementById('entry');
elEntry.onsubmit=entry;
I have tried:
Adding in a prevent default:
window.event.preventDefault();
doing this through an event Listener:
elEntry.addEventListener('submit',entry,false);
using innerHTML to post the message:
elMsg.innerHTML = "
At present all that happens is that the pushing submit reloads the page - with no indication of any text being posted anywhere.

One issue is that you have a typo, where getElementById capitalized the D at the end.
Another is that preventDefault() should be called on the form element, not the input.
Here's a working example that corrects those two mistakes.
function entry(event) {
var elOwner = document.getElementById('owner');
var elMsg = document.getElementById('feedback');
elMsg.textContent = 'hello';
event.preventDefault();
}
var entryForm = document.getElementById('entry').form;
entryForm.onsubmit = entry;
<form method="post" action="">
<label for="owner">Input Owner: </label>
<input type="text" id="owner" />
<div id="feedback"></div>
<input type="submit" value="enter" id="entry" />
</form>
I also defined a event parameter for the handler. I don't remember is window.event was ever standardized (it probably was), but I'd prefer the parameter.
Be sure to keep your developer console open so that you can get information on errors that may result from typos.

var elEntry = document.getElementById('entry');
elEntry.addEventListener("click", function(e) {
e.preventDefault();
var elMsg = document.getElementById('feedback');
elMsg.textContent = 'hello';
});
<form method="post" action="">
<label for="owner">Input Owner: </label>
<input type="text" id="owner" />
<div id="feedback"></div>
<input type="submit" value="enter" id="entry" />
</form>

Event will not trigger

I have a form that has multiple inputs. One input is where user can input an ID. I need to verify the ID is unique. I want to call a JavaScript function for a onchange event. However, I can't get it to trigger. I have a console.log but it never hits when I make a change in the input so I am doing something wrong.
This is the function I am trying to call on the on change
function checkUniqueID() {
console.log("here");
var $counter = 0;
var tag = document.forms["userform"]["new_id"].value;
while ($counter < $totalItems) {
}
};
<div class="six wide field">
<label for="ID">ID</label>
<input type="text" id="new" name="new_id" placeholder="ID" onchange="checkUniqueID()">
</div>
I can't even get the console.log ("here") to trigger

The onchange HTML attribute triggers when the input loses focus.
So, if you correctly have your input#new_id inside a form like this:
<form name="userform">
<div class="six wide field">
<label for="ID">ID</label>
<input type="text" id="new" name="new" placeholder="ID">
</div>
</form>
Adding an eventListener in your script file would be enough.
document.userform.new_id.onchange=function(){
alert("ID changed to: "+this.value);
};
With jQuery would be as easy as:
$("#new").change(function(){
alert("ID changed to: "+$(this).value;
}
Here is a working fiddle:
https://jsfiddle.net/edbL3kgp/

validating a form using jQuery

I've tried, I've researched, and I still can't figure out how to validate this form using jQuery. I've even tried to check out the jQuery API and I had no luck with it. This shouldn't be as hard as it seems. There are a few id's that i'm not using yet because I want to get what I have so far working before I continue. The best I could find for validating emails is just straight up JavaScript. Here's my code.
$(document).ready(function(){
$("#sendForm").click(function(){
var validForm=true; //set valid flag to true, assume form is valid
//validate customer name field. Field is required
if($("#custName").val()) {
$("#custNameError").html(""); //field value is good, remove any error messages
} else {
$("#custNameError").html("Please enter your name.");
validForm = false;
}
//validate customer phone number. Field is required, must be numeric, must be 10 characters
var inPhone = $("#custPhone").val(); //get the input value of the Phone field
$("#custPhoneError").html(""); //set error message back to empty, assume field is valid
if(!inPhone) {
$("#custPhoneError").html("Please enter your phone number.");
validForm = false;
} else {
//if( !$.isNumeric(inPhone) || Math.round(inPhone) != inPhone ) //if the value is NOT numerice OR not an integer. Rounding technique
if( !$.isNumeric(inPhone) || (inPhone % 1 != 0) ) //if the value is NOT numerice OR not an integer. Modulus technique
{
$("#custPhoneError").html("Phone number must be a number.");
validForm = false;
} else {
if(inPhone.length != 10) {
$("#custPhoneError").html("Phone number must have 10 numbers");
validForm = false;
}
}
}
//ALL VALIDATIONS ARE COMPLETE. If all of the fields are valid we can submit the form. Otherwise display the errors
if(validForm) {
//all values are valid, form is good, submit the form
alert("Valid form will be submitted");
//$("#applicationForm").submit(); //SUBMIT the form to the server
} else {
//form has at least one invalid field
//display form and associated error messages
alert("Invalid form. Display form and error messages");
}
}); //end sendform.click
}); //end .ready
function isEmail(email) {
var regex = /^([a-zA-Z0-9_.+-])+\#(([a-zA-Z0-9-])+\.)+([a-zA-Z0-9]{2,4})+$/;
return regex.test(email);
}
label {
width:150px;
display:inline-block;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<h2></h2>
<h3>Form Validation Project - Complaint Form</h3>
<form id="form1" name="form1" method="post" action="">
<p>Please enter the following information in order to process your concerns.</p>
<p>
<label for="custName">Name:</label>
<input type="text" name="custName" id="custName" />
<span id="custNameError" class="errorMsg"></span>
</p>
<p>
<label for="custPhone">Phone Number: </label>
<input type="text" name="custPhone" id="custPhone" />
<span id="custPhoneError" class="errorMsg"></span>
</p>
<p>
<label for = "email">Email:</label>
<input type = "text" name = "emailAdd" id = "emailAdd" />
<span id = "emailError" class = "emailError"></span>
</p>
<p>Please Select Product Group:</p>
<p>
<label>
<input type="radio" name="custProducts" value="books" id="custProducts_0" />
Books
</label>
<br />
<label>
<input type="radio" name="custProducts" value="movies" id="custProducts_1" />
Movies
</label>
<br />
<label>
<input type="radio" name="custProducts" value="electronics" id="custProducts_2" />
Consumer Electronics
</label>
<br />
<label>
<input type="radio" name="custProducts" value="computer" id="custProducts_3" />
Computer
</label>
<br />
</p>
<p>Description of problem: (Limit 200 characters)</p>
<p>
<label for="custComplaint"></label>
<textarea name="custComplaint" id="custComplaint" cols="45" rows="5"></textarea>
</p>
<p>
<input type="submit" name="button" id="button" value="File Complaint" />
<input type="reset" name="button2" id="button2" value="Reset" />
</p>
</form>
<p> </p>

$("#button").click(function(e){
e.preventDefault(); // you need to stop the initial event to have a chance to validate
var validForm=true;
// etc...

You can use jquery.validate.js to validate your forms , it will overcome all your manual efforts to create the validation rules also it is providing the various predefined rules like required,email, minlength and maxlength, etc. So, it will be easier for you to achieve what you need very easily.
https://jqueryvalidation.org/

I have a simple jquery form validation and submission package - see if that's of any help - it's easy to install and you can customise quite a few things: https://github.com/sebastiansulinski/ssd-form

Just to get you started, your submit control in the html has id "button", so you should use $('#button').click, not $('#sendForm').click.
Also, if you want to stay on the page (like to do validations, show errors, etc), you have to prevent the form from submitting automatically when the button is clicked. There are lots of ways to do this, but the easiest way is to just change your button type from submit to button. Ie, replace this:
<input type="submit" name="button" id="button" value="File Complaint" />
with this:
<input type="button" name="button" id="button" value="File Complaint" />
------
That should get you started, at least your code will run, you can use console.log to debug, etc. Good luck.
UPDATE
I should add that if you take my advice, the form will never submit on it's own - that is good if some validation fails and you want to stay on the page and give some error feedback to the user.
When you do want the form to submit, you have to make it happen yourself. Again, there are lots of ways to do this, but the simplest one is probably:
$('#form1').submit();

Why this code is not generating any alert message

Here i have written some that is for validation on form in html and javascript
<!DOCTYPE html>
<html>
<body>
<form name="registration">
<input style="font-size:16px;" type="text" name="Name" placeholder="Full Name" onchange="checkName()" required />
</form>
<script>
function checkName()
{
var uname=document.registration.Name.value;
var letters = /^[A-Za-z]+$/;
if(uname.value.match(letters))
{
alert('fg');
}
else
{
alert('Username must have alphabet characters only');
//uname.focus();
}
}
</script>
</body>
</html>
Please describe why it is not working?

The problem is that you're trying to get the value property TWICE. Like such:
var uname=document.registration.Name.value;
if(uname.value.match(letters))
Your uname variable already contains the value, so you don't need to get it again. Change your if statement to this...
if (uname.match(letters))
And it works just fine :)

Using onchange with input type = "text" is quite uncommon
onchange event usually occurs only after you leave (blur) the control.
onchange is mainly associated with change of select element.
For your case it is better to use keydown, keyup and keypress events as well.
HTML
<input style="font-size:16px;" type="text" name="Name" placeholder="Full Name" onkeyup="checkName()" required />
Jsfiddle

How can I show input fields only when previous input has a valid value?

I have a form that requires between 3 and 10 text input items. When the form first loads it will show 3 inputs (minimum).
I'd like to efficiently show input rows as the previous row has a valid value (let's assume greater than 3 characters for example). So if you fill out the first 3, you will automatically see a 4th optional input row.
Can you help me loop through this quick list efficiently in jQuery?
HTML:
<input type="text" class="item_1" name="item_1">
<input type="text" class="item_2" name="item_2">
<input type="text" class="item_3" name="item_3">
<input type="text" class="item_4" name="item_4">
<input type="text" class="item_5" name="item_5">
<input type="text" class="item_6" name="item_6">
<input type="text" class="item_7" name="item_7">
<input type="text" class="item_8" name="item_8">
<input type="text" class="item_9" name="item_9">
<input type="text" class="item_10" name="item_10">
CSS:
.item_4,.item_5,.item_6,.item_7,.item_8,.item_9,.item_10 { display:none }

This is pretty simple - you shouldn't even need a loop if you let jQuery's chaining do the work. I'd do something like:
$("#myform input").change(function(){ //If an input in your form is changed,
if ($(this).val() == 42){ //replace with your validation logic :)
$(this).next('input').show(); //This shows the next sibling element to the triggering element
} else { //but if it fails validation...
$(this).nextAll('input').hide().val(""); //hide them and delete the contents to stop the form from uploading invalidated data!
}
});
This does what you asked, and for bonus points it hides and empties later boxes if their predecessors are later changed to be invalid.