Develop Reference

Using JavaScript to check for user-input

I'm submitting a form with input text to my server through my web client. What I'm trying to do is to check whether the user has passed in text into the input field before sending the form by hitting the submit button.
What I have tried so far:
var form = document.getElementById("id");
document.getElementById("id").addEventListener("click", function() {
var input = document.getElementById("content").value;
if (input == "") {
alert("write something in the textfield");
} else {
form.submit();
}
});
<form action="" method="post" id="id">
<input type="text" name="name" id="content">
<button type="submit" id="submit-id">submit text</button>
</form>
Any good tips on how to do this?

You want preventDefault on the submit event
document.getElementById("id").addEventListener("submit", function(e) {
const input = document.getElementById("content").value;
if (input.trim() === "") {
alert("write something in the textfield");
e.preventDefault()
}
});
<form action="" method="post" id="id">
<input type="text" name="name" id="content">
<button type="submit" id="submit-id">submit text</button>
</form>
Alternatively just add required attribute - no need for script:
<form action="" method="post" id="id">
<input type="text" name="name" id="content" required>
<button type="submit" id="submit-id">submit text</button>
</form>

you can use the simple code snippet instead :
<form action="" method="post" id="id">
<input type="text" name="name" id="content" required>
<button type="submit" id="submit-id">submit text</button>
</form>

function submitIt(e) {
var formData = new FormData(e);
var object = {};
formData.forEach(function(value, key) {
object[key] = value;
});
if (object.name == "") {
alert("null");
} else {
alert("ok");
return true;
}
return false;
}
<form onsubmit="return submitIt(this)">
<input type="text" name="name">
<button>submit text</button>
</form>

How can i validate and alert if the phone has incorrect input?

The phone number and the email must be valid.
This is a basic popup contact form without the phone number validation. I would like to validate the phone number. I heard about regex but i´m not sure how to implement in the code.
Since i don´t understand javascrip yet i hope you can help me.
<form action="#" method="post" id="form">
<h2>Contact Us</h2><hr/>
<input type="text" name="company" id="company" placeholder="Company"/>
<input type="text" name="name" id="name" placeholder="Name"/>
<input type="text" name="email" id="email" placeholder="Email"/>
<input type="text" name="phone" id="email" placeholder="Phone"/>
<a id="submit" href="javascript: check_empty()">Send</a>
</form>
function check_empty(){
if(document.getElementById('company').value == ""
|| document.getElementById('name').value == ""
||document.getElementById('email').value == ""
||document.getElementById('phone').value == "" ){
alert ("Please, fill the fields!");
}
else {
document.getElementById('form').submit();
}
}
//function to display Popup
function div_show(){
document.getElementById('abc').style.display = "block";
}
//function to check target element
function check(e){
var target = (e && e.target) || (event && event.srcElement);
var obj = document.getElementById('abc');
var obj2 = document.getElementById('popup');
checkParent(target)?obj.style.display='none':null;
target==obj2?obj.style.display='block':null;
}
//function to check parent node and return result accordingly
function checkParent(t){
while(t.parentNode){
if(t==document.getElementById('abc'))
{
return false
}
else if(t==document.getElementById('close'))
{
return true
}
t=t.parentNode
}
return true
}

How to submit a form from script

I have a simple form:
<form id="form" method="post" action="email.php">
<input id="name" name="name" type="text" placeholder="Name" />
<input name="email" id="email" type="text" placeholder="Email" />
<textarea name="text" id="msg" placeholder="Comment"></textarea>
<input type="button" value="SUBMIT" id="submit" onclick="empty()"/>
</form>
and an empty() function for checking if all inputs are there:
function empty(){
var x; var y; var z;
x = document.getElementById("name").value;
y = document.getElementById("email").value;
z = document.getElementById("msg").value;
if (x == "" || y == "" || z == "") {
document.getElementById("errors").innerHTML = "All inputs must be present before submitting.";
return false;
}else{
document.form.submit(); /*this doesn't work*/
}
}
But I can't seem to get the form to submit...

The problem is with the button type. Try this:
<script>
function empty() {
var x;
var y;
var z;
x = document.getElementById("name").value;
y = document.getElementById("email").value;
z = document.getElementById("msg").value;
if (x == "" || y == "" || z == "") {
document.getElementById("errors").innerHTML = "All inputs must be present before submitting.";
return false; // the only reason this worked previously is that the input type was wrong so the form didn't submit
} else {
return true; // return true instead of trying to submit the form with js
}
}
</script>
<form id="form" method="post" action="email.php">
<input id="name" name="name" type="text" placeholder="Name" />
<input name="email" id="email" type="text" placeholder="Email" />
<textarea name="text" id="msg" placeholder="Comment"></textarea>
<input type="submit" value="SUBMIT" id="submit" onclick="return empty();" />
<!-- change the button type to submit and return the value from the empty function (false will prevent the default action of the button - stop the form submitting, true will allow the form to submit) -->
</form>
<div id="errors"></div>
Noticed this doesn't work as a snippet so this is it working in a fiddle

You need to define name of the form.After define this form can be submit using javascript.
To check example you can follow this example-
<form name="myform" action="handle-data.php">
Search: <input type='text' name='query' />
Search
</form>
<script type="text/javascript">
function submitform()
{
document.myform.submit();
}
</script>

Show alert (Text Field is empty) on submit Html/JavaScript

How to get an Alert on Submit when I left a TextBox empty And It Should Turn To the Next page on submit.
Must Reply,
Thank You.

You can try this :
HTML :
<form action="" method="POST" id="myForm">
<input id="myInput" type="text" />
<input type="submit" />
</form>
(Replace the action attribute by the url of your destination page, the one you call the "next page").
JS (without jQuery):
var myForm = document.querySelector('#myForm');
var myInput = document.querySelector('#myInput');
myForm.addEventListener('submit', function(pEvent) {
if(myInput.value === '') {
pEvent.preventDefault(); //Prevents the form to be sent
alert('Ho! Stop!');
//Do whatever you want
}
});
JS (with jQuery) :
var myForm = $('#myForm');
var myInput = $('#myInput');
myForm.on('submit', function(pEvent) {
if(myInput.val() === '') {
pEvent.preventDefault(); //Prevents the form to be sent
alert('Ho! Stop!');
}
});
Demo : http://jsfiddle.net/af9qvkmp/9/

Here is the demo, based on jQuery!
HTML
<form action="" method="POST" id="form">
<input id="input1" type="text" />
<input id="input2" type="text" />
<input id="input3" type="text" />
<input id="input4" type="text" />
<input id="input5" type="text" />
<input type="submit" />
</form>
JS
$(function() {
$('#form').on('submit', function(event) {
var isError = false;
$(this).find('input[type="text"]').each(function() {
if($(this).val() == '') {
console.log($(this));
isError = true;
return false;
}
});
if(isError) {
event.preventDefault();
alert("Got Error");
} else {
// Submit the form
}
});
});

In form tag write
<form action="" method="post" enctype="multipart/form-data" onsubmit="return checkform(this);">
This is your input field
<input type="text" name="reviewValue" value="" id='starRate2' required>
Javascript Code:
<script language="JavaScript" type="text/javascript">
function checkform ( form ){
if (form.reviewValue.value == "") {
alert( "Please choice your Rating." );
form.reviewValue.focus();
return false ;
}
return true ;
}
</script>

How to make a required field be invisible if valid?

I have this kind of html:
<form method="post" action="register">
<input type="text" name="name" required />
<button>Next</button>
</form>
When I click the Next button, I want to hide the Name field, but only if it is valid(not empty) and I don't want to submit the form. How can I do this with plain JavaScript?
If you know a way with jQuery, please write that too. Thanks.

Try this:
$('button').click(function() {
var check = $('#name').val();
if (check == '') {
$('#name').hide();
}
})
If the input has no content, it will be hidden.

document.querySelector('form').addEventListener('submit', function (e) {
e.preventDefault();
var input = e.target.firstElementChild;
if(!input.validity.valueMissing) {
input.style.display = 'none';
}
}, false);
<form method="post" action="register">
<input type="text" name="name" required />
<button>Next</button>
</form>

Assuming that you will change "form button" for the ID of the button, and "form input" for the ID of the input. The jQuery code would be something like this:
$("form button").click(function() {
if ($("form input").val() != "")
$("form input").hide();
});

Try this:
<form method="post" action="register">
<div id="steps1">
<input id="txtname" type="text" placeholder="enter name here" name="name" />
<input id="btnNext" type="button" value="next" />
</div>
<div id="complete" style="display:none;">
<input type="text" name="age" placeholder="enter age here" />
<input type="submit" value="submit" />
</div>
</form>
$(document).ready(function () {
$("#btnNext").click(function () {
if ($("#txtname").val() != "") {
$("#steps1").hide();
$("#complete").show();
}
});
});

In jQuery:
$("button").click(function() {
if ($('input[name=name]').val() != '') {
$('input[name=name]').fadeOut(); // Or hide, or css('display', 'none')
}
});

Make class e.g. "validate", which you can attach to your form after clicking Next.
Then in CSS:
.validate input:valid {
display: none;
}

Try onsubmit event:
var validate = function(form) {
var toSubmit = true;
if (form.name.value) { //has some text
form.name.style.display = "none"; //hide the input field
} else {
toSubmit = false;
}
return toSubmit;
};
<form method="post" action="register" onsubmit='return validate(this);'>
<input type="text" name="name" required />
<button>Next</button>
</form>
EDIT
Try blur event:
var validate = function(box) {
if (!box.value) {
alert('This field is required');
box.focus();
}
};
<form method="post" action="register">
<input type="text" name="name" onblur='validate(this);' />
<button>Next</button>
</form>

Read these to understand the code and why.
document.querySelector
EventTarget.addEventListener
onsubmit
event.preventDefault
Constraint validation HTML5
document.querySelector('form').addEventListener('submit', function (e) {
e.preventDefault();
var input = e.target.firstElementChild;
if(!input.validity.valueMissing) {
input.style.display = 'none';
}
}, false);
<form method="post" action="register">
<input type="text" name="name" required />
<button>Next</button>
</form>