Javascript form validation - javascript

I'm trying to have two functions checking each form input, one for onchange() and the other for onkeypress(); my reason for this would be to show if the input was valid once you leave the input field using onchange() or onblur(), and the I also wanted to check if the input field was ever empty, to remove the message indicating that bad input was entered using onkeypress() so that it would update without having to leave the field (if the user were to delete what they had in response to the warning message.)
It simply isn't working the way I intended, so I was wondering if there was something obviously wrong.
My code looks like this:
<form action="database.php" method = post>
Username
<input type='text' id='un' onchange="checkname()" onkeypress="checkempty(id)" />
<div id="name"></div><br>
.....
</form>
And the Javascript:
<script type="text/javascript">
function checkname() {
var name = document.getElementById("un").value;
var pattern = /^[A-Z][A-Za-z0-9]{3,19}$/;
if (name.search(pattern) == -1) {
document.getElementById("name").innerHTML = "wrong";
}
else {
document.getElementById("name").innerHTML = "right!";
}
}
function checkempty(id) {
var temp = document.getElementById(id).value;
if (!temp) {
document.getElementById("name").innerHTML = '';
}
}
</script>

Per your clarification in the comments, I would suggest using the onkeyup event instead of onkeypress (onkeypress only tracks keys that generate characters - backspace does not). Switching events will allow you to validate when the user presses backspace.
Here's a working fiddle.
Edit:
See this SO question for further clarification: Why doesn't keypress handle the delete key and the backspace key

This function should below should check for empty field;
function checkempty(id) {
var temp = document.getElementById(id).value;
if(temp === '' || temp.length ===0){
alert('The field is empty');
return;
}
}
//This should work for check name function
function checkname() {
var name = document.getElementById("un").value;
var pattern = /^[A-Z][A-Za-z0-9]{3,19}$/;
if (!name.test(pattern)) {
document.getElementById("name").innerHTML = "wrong";
}
else {
document.getElementById("name").innerHTML = "right!";
}
}

Related

Javascript form validation code looping

The following code loops when the page loads and I can't figure out why it is doing so. Is the issue with the onfocus?
alert("JS is working");
function validateFirstName() {
alert("validateFirstName was called");
var x = document.forms["info"]["fname"].value;
if (x == "") {
alert("First name must be filled out");
//return false;
}
}
function validateLastName()
{
alert("validateLastName was called");
var y = document.forms["info"]["lname"].value;
if (y == "") {
alert("Last name must be filled out");
//return false;
}
}
var fn = document.getElementById("fn");
var ln = document.getElementById("ln");
fn.onfocus = validateFirstName();
alert("in between");
ln.onfocus = validateLastName();
There were several issues with the approach you were taking to accomplish this, but the "looping" behavior you were experiencing is because you are using a combination of alert and onFocus. When you are focused on an input field and an alert is triggered, when you dismiss the alert, the browser will (by default) re-focus the element that previously had focus. So in your case, you would focus, get an alert, it would re-focus automatically, so it would re-trigger the alert, etc. Over and over.
A better way to do this is using the input event. That way, the user will not get prompted with an error message before they even have a chance to fill out the field. They will only be prompted if they clear out a value in a field, or if you call the validateRequiredField function sometime later in the code (on the form submission, for example).
I also changed around your validation function so you don't have to create a validation function for every single input on your form that does the exact same thing except spit out a slightly different message. You should also abstract the functionality that defines what to do on each error outside of the validation function - this is for testability and reusability purposes.
Let me know if you have any questions.
function validateRequiredField(fieldLabel, value) {
var errors = "";
if (value === "") {
//alert(fieldLabel + " must be filled out");
errors += fieldLabel + " must be filled out\n";
}
return errors;
}
var fn = document.getElementById("fn");
var ln = document.getElementById("ln");
fn.addEventListener("input", function (event) {
var val = event.target.value;
var errors = validateRequiredField("First Name", val);
if (errors !== "") {
alert(errors);
}
else {
// proceed
}
});
ln.addEventListener("input", function (event) {
var val = event.target.value;
var errors = validateRequiredField("Last Name", val);
if (errors !== "") {
alert(errors);
}
else {
// proceed
}
});
<form name="myForm">
<label>First Name: <input id="fn" /></label><br/><br/>
<label>Last Name: <input id="ln"/></label>
</form>
Not tested but you can try this
fn.addEventListener('focus', validateFirstName);
ln.addEventListener('focus', validateLastName);

Jquery Error validation insert div using after() but cannot remove

I want to show error validation messages next to the textbox. For that, I have used after() function and inserted a div. But the div gets appended again and again whenever the field is invalid. I just want it once. Can anybody help me with it?
Here's my code:
$(document).ready(function()
{
$("#name").blur(function()
{
var name = $("#name").val();
var txt= /^[A-Za-z\s]+$/i ;
if((txt.test(name) != true))
{
$("#name").after('<div id="one" style="color:#00aaff;">Invalid Name</div>');
$("#one").empty();
}
else
{
$("#one").remove();
}
});
});
You could use HTML 5 field's validity which is the standard.
<input type="text" pattern="[a-zA-Z]+"
oninvalid="setCustomValidity('Your error message here')"
onchange="setCustomValidity('')" />
You should use additional variable to store your state. Try this logic.
$(document).ready(function() {
var flag = false;
$("#name").blur(function() {
var name = $("#name").val();
var txt = /^[A-Za-z\s]+$/i;
if (!txt.test(name) && !flag) {
$("#name").after('<div id="one" style="color:#00aaff;">Invalid Name</div>');
flag = true;
}
else if (flag && txt.test(name)) {
flag = false
$("#one").remove();
}
});
});

dynamically check form field values javascript

Is it possible to check the form field values dynamically with javascript only.
For example if I have form field for username and when the user enters their chosen username it checks whether this username is available and pops up an alert box or shows a message on the screen based on the result.
all of this is done without clicking any button. and the data is stored in an array.
Thanks in advance. Im trying to achieve this only by using javascript.
var username = document.getElementById('username');
var goBtn = document.getElementById('check');
var output = document.getElementById('output');
var usernames = ['bob', 'sally', 'alice', 'roy', 'kate', 'phil'];
function showResult() {
output.innerHTML = usernames.join(', ');
}
function checkUsername() {
if (usernames.indexOf(username.value) < 0) {
usernames.push(username.value);
username.value = '';
} else {
alert('That username is already taken. Try again.');
}
showResult();
}
goBtn.onclick = checkUsername;
showResult();
<label for="username">Name:</label>
<input id="username" name="username" placeholder="username">
<button id="check">Go</button>
<div id="output"></div>
may be this is what you want
// usernameArray contains all the usernames that can't be used
var usernameArray = ['username1','username2','username3'];
// i'm using .kyup() method to get a dynamic result so whenever the user type a letter or
// something else (just one caracter) we check that value against our usernameArray list
$('#username').keyup(function(){
var value = $(this).val();
if(usernameArray.indexOf(value) >= 0){
alert('sorry, try another username ');
}else{
alert('good, you can use this username it is available');
}
});

How do I use javascript to prevent form submission because of empty fields?

How do I make a script in javascript to output an error and prevent form submission with empty fields in the form? Say the form name is "form" and the input name is "name". I have been having some trouble with PHP not always handling the empty fields correctly, so I would like this as a backup. Any help is appreciated, thanks.
HTML Code :-
<form name='form'>
<input type="button" onclick="runMyFunction()" value="Submit form">
</form>
Javascript Code :-
function runMyFunction()
{
if (document.getElementsByName("name")[0].value == "")
{
alert("Please enter value");
}
else
{
var form= document.getElementsByName("form")[0];
form.submit();
}
}
Claudio's answer is great. Here's a plain js option for you. Just says to do nothing if field is empty - and to submit if not.
If you need to validate more than one, just add an && operator in the if statement and add the same syntax for OtherFieldName
function checkForm(form1)
{
if (form1.elements['FieldName'].value == "")
{
alert("You didn't fill out FieldName - please do so before submitting");
return false;
}
else
{
form1.submit();
return false;
}
}
This is untested code but it demonstrates my method.
It will check any text field in 'form' for empty values, and cancel the submit action if there are any.
Of course, you will still have to check for empty fields in PHP for security reasons, but this should reduce the overhead of querying your server with empty fields.
window.onload = function (event) {
var form = document.getElementsByName('form')[0];
form.addEventListener('submit', function (event) {
var inputs = form.getElementsByTagName('input'), input, i;
for (i = 0; i < inputs.length; i += 1) {
input = inputs[i];
if (input.type === 'text' && input.value.trim() === '') {
event.preventDefault();
alert('You have empty fields remaining.');
return false;
}
}
}, false);
};
Attach an event handler to the submit event, check if a value is set (DEMO).
var form = document.getElementById('test');
if (!form.addEventListener) {
form.attachEvent("onsubmit", checkForm); //IE8 and below
}
else {
form.addEventListener("submit", checkForm, false);
}
function checkForm(e) {
if(form.elements['name'].value == "") {
e.preventDefault();
alert("Invalid name!");
}
}

JQuery Validation for Two Password Fields

Two entered passwords should be the same, and I want to display a notification when they're not matching. The target is to display the notification during typing and not after pressing the save Button.
I am new to javascript and I have also tried the functionname function() notation.
following js:
function updateError (error) {
if (error == true) {
$(".error").hide(500);
}else{
$(".error").show(500);
}
};
function checkSame() {
var passwordVal = $("input[name=password-check]").val();
var checkVal = $("input[name=password]").val();
if (passwordVal == checkVal) {
return true;
}
return false;
};
document.ready(function(){
$("input[name=password-check]").keyup(function(){updateError(checkSame());});
$("input[name=password]").keyup(function(){updateError(checkSame());});
});
and HTML:
#Html.Password("password")
#Html.Password("password-check")
<span class="error">Errortext</span> </td></tr>
but it doesn't works..
Thx!
Edit:
Now i've changed the JS code to:
$("input[name=password-check]").keyup(function(){updateError(checkSame());});
$("input[name=password]").keyup(function(){updateError(checkSame());});
--> now it works, but only once, after the user typed a matching password, validation stops working
Solved, problem was Quoting:
$("input[name='password-check']").keyup(function(){updateError(checkSame());});
$("input[name='password']").keyup(function(){updateError(checkSame());});
You are doing opposite
if (error == true) {
    $(".error").show(500);
}else{
 $(".error").hide(500);
}
Edit as per comment :
Try placing name within quotes like
$("input[name='password-check']").keyup(function(){updateError(checkSame());});
$("input[name='password']").keyup(function(){updateError(checkSame());});
In the checkSame, you may want to use indexOf to check if passwordVal contains checkVal since when typing, the password is not equal yet.
if (passwordVal.indexOf(checkVal)>-1 || checkVal.indexOf(passwordVal)>-1 ) {
return true;
}
As int2000 said, fire the checkSame on keyup seems weird, but if it's what you want, OK.
Try to change your checkSame function as follows:
function checkSame() {
var passwordVal = $("input[name=password-check]").val();
var checkVal = $("input[name=password]").val();
if (passwordVal == checkVal) {
return false;
}
return true;
};
Remember that you're passing the result of checkSame to updateError, so if the passwords are the same you have no error.

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