Javascript form validating and prevent submission - javascript

How can I prevent submision if in my text field are entered just specific characters <>{} and not all of special characters? I'm losing my mind :/

I think you are looking for regex expression. Let me know if it's helpful
$(":input").each(function() {
var input = $(this).val();
var regex = new RegExp("^[a-zA-Z]+$");
if(regex.test(input)) {
alert("true");
} else {
alert("false");
return false;
}
})

I don't have an exact answer as you didn't post any sample code. I can only point you to this article https://javascript.info/bubbling-and-capturing which explain how events bubbling works. A solution will be to use event.stopPropagation() in case the validation doesn't pass.
Here an working ex:
<!DOCTYPE html>
<html>
<head>
<script>
function validateForm() {
const regex = new RegExp('^[a-zA-Z]+$');
const input = document.forms['someForm']['somename'].value;
if (regex.test(input)) {
console.log("true");
} else {
console.log("false");
return false;
}
}
</script>
</head>
<body>
<form name="someForm" onsubmit="return validateForm()" method="post">
Name: <input type="text" name="somename">
<input type="submit" value="Submit">
</form>
</body>
</html>

Related

Javascript live validation

I have a very simple HTML/JavaScript form that I am working on for coursework, I have got it to work however i would like it to validate the input as the user types (my validation appears below the text field) how can I achieve this? My code is as follows:
<!DOCTYPE html>
<html>
<head>
<script class="jsbin" src="http:ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"> </script>
<meta charset=utf-8 />
<title>Email Validation</title>
</head>
<body>
<form onsubmit='validate(); return false;'>
<p>Enter an email address:</p>
<input id='email' placeholder="example#example.com" size="21">
<button type='submit' id='validate'>Submit</button>
</form>
<br />
<h2 id='result'></h2>
<script>
function validateEmail(email) {
var re = /^(([^<>()[\]\\.,;:\s#\"]+(\.[^<>()[\]\\.,;:\s#\"]+)*)|(\".+\"))#((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;
return re.test(email);
}
function validate() {
$("#result").text("");
var email = $("#email").val();
if (validateEmail(email)) {
$("#result").text(email + " is valid");
$("#result").css("color", "green");
} else {
$("#result").text(email + " is not valid");
$("#result").css("color", "red");
}
return false;
}
$("form").bind("submit", validate);
</script>
</body>
</html>
For methods not using jQuery, in case you're interested, there's another Stack Overflow question here: On Input Change Event.
There are many ways to do what you want listed there, but in this case you could do something like this:
var input = document.querySelector('input');
input.addEventListener('input', function()
{
// Check input.value for what you're looking for here
});
See the jsFiddle that Drew Noakes' made in that other page for an example.
But, since you're using jQuery, then Nicholas Kyriakides's suggestion is the way to go.

check text box value is according to a prefix

I have text box.
Users can enter Student Id into that.
Student id is in this format DIP0001.
First three letters should be DIP and the remaining 4 digits should be numeric and can only upto 4 characters.
So how can I check whether entered data is in this format using javascript.
Please help.....
You could build a regular expression pattern and test it against that value to see if it matches that exact pattern.
HTML FILE:
<!DOCTYPE html>
<html lang="en">
<head>
<title>Title</title>
</head>
<body>
<label for="studentId">Student ID</label>
<input id="studentId" type="text">
<button id="btn" type="button">Validate</button>
// Embedded script so that you don't have to load an external file
<script>
var input = document.getElementById('studentId');
var btn = document.getElementById('btn');
var pattern = /DIP+\d{1,3}/g;
btn.addEventListener('click', function(){
if(pattern.test(input.value)) {
alert('It enter code here`atches!');
}else {
alert('It does not match!');
}
});
</script>
</body>
</html>
JS FILE:
// This pattern looks something like this: DIP0000
var pattern = /DIP+\d{1,3}/g;
// studentId is the ID of the input field that contains the Student ID
var studentIdInput = document.getElementById('studentId');
// Check the pattern against the provided Student ID
if(pattern.test(studentIdInput.value)) {
alert('It matches the pattern!');
}
EDIT 1: I have built the functionality in the following JSFiddle: http://jsfiddle.net/vldzamfirescu/QBNrW/
Hope it helps!
EDIT2: I have updated the JSFiddle to match any other combinations up to 4 digits; check it out: http://jsfiddle.net/vldzamfirescu/QBNrW/1/ Let me know if it solved your problem!
try this code
<html>
<head>
<script>
function validate(val) {
if (val.value != "") {
var filter = /^[DIP]|[dip]+[\d]{1,4}$/
if (filter.test(val.value)) { return (true); }
else { alert("Please enter currect Student Id"); }
val.focus();
return false;
}
}
</script>
</head>
<body>
<input id="Text1" type="text" onblur="return validate(this);" />
</body>
</html>
Use Regular Expresions.
If found a valid Student ID, the pattern will return true:
function validateStudentId(id) {
var re = /DIP[0-9]{4}/;
return re.test(id);
}
// Edited for use with a click event:
document.getElementById('button').addEventListener('click', function(){
if( validateStudentId(document.getElementById('textBox').value) ){
alert('correct');
}else{
alert('invalid ID');
}
});

JavaScript Is Text Box Empty?

How can I check if a input field is empty in JavaScript when submitting the form?
html:
<input type="text" name="start_name" id="start_name">
Refer to http://www.w3schools.com/js/js_form_validation.asp
Have your form tag as
<form name="myForm" action="demo_form.asp" onsubmit="return validateForm()" method="post">
Next, have a javascript function
<script>
function validateForm()
{
var x=document.forms["myForm"]["start_name"].value;
if (x==null || x=="")
{
alert("Start name must be filled out");
return false;
}
}
</script>
var start_name = document.getElementById('start_name');
if( start_name.value.length > 0 ){
// Then there is something there.
}
Try.
<script type="text/javascript">
function checkme()
{
var inputVal = document.getElementById("start_name").value;
if(inputVal == "")
{
//code
}
}
</script>
<form action="" method="post" onSubmit = "checkme();">
<input type="text" name="start_name" id="start_name">
</form>
Just checking 'if (x==null || x=="")' is not enough to validate empty text box. Go for RegEx to check empty text box.
/^\s*[0-9a-zA-Z][0-9a-zA-Z ]*$/
Ensures that at least one character is not whitespace and is of one of the allowed characters.
Use /[a-z]/i as this regex will only match if there is at least one alphabetical character.
<form action="someActionUrl" onsubmit="return validate('first_name')">
<input id="first_name" name="first_name" />
</form>
<script>
function validate(inputId){
var val = document.getElementById(inputId).value;
if(val.length>0){
// do something
return true;
}
return false;
}
</script>
try this:
var x = document.getElementById("start_name");
if(x.value== "")
{
//your restriction code comes here
}
else
{
//go ahead!
}
Note: please check for syntax if its proper.i am writing the code here directly,haven't checked it on IDE.

Validating an e-mail address using regex

I am trying to validate e-mail addresses on my website and I have been trying to code up a demo of how e-mail validation would work with JavaScript. What I am trying to do is pass in the value of the e-mail address entered by the user to the validateEmail function and then print out 'valid' or 'invalid' in the div with the id 'result'. Because I am relatively new to JavaScript, I am not sure how to accomplish this and was wondering it if someone could show me an example of how to do this?
<head>
<title>Practice</title>
<script type="text/javascript">
function validateEmail(email) {
var re = /^(([^<>()[\]\\.,;:\s#\"]+(\.[^<>()[\]\\.,;:\s#\"]+)*)|(\".+\"))#((\[[0-9{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;
return re.test(email);
}
</script>
</head>
<body>
<form action="post" method="practice.php">
e-mail: <input id="email" type="text" onblur="validateEmail(execute(document.getElementById('email').value))" />
<div id="result"></div>
</form>
</body>
First of all you don't need to use execute method and can get value from this context:
validateEmail( this.value )
Then modify your function to print result:
function validateEmail(email) {
var re = /^(([^<>()[\]\\.,;:\s#\"]+(\.[^<>()[\]\\.,;:\s#\"]+)*)|(\".+\"))#((\[[0-9{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;
if(re.test(email)) {
document.getElementById('result').innerHTML = 'valid';
} else {
document.getElementById('result').innerHTML = 'invalid';
}
}

Having issue to validate form using JavaScript

My following JavaScript is not working:
<script type="text/javascript">
function checkDetails(search)
{
var search = documment.getElementById('query');
if(search.value ==''||search.value==null)
{
alert('No search criteria entered');
query.focus;
return false;
}
}
</script>
</head>
<body>
<form name="search" action ="123.php" onSubmit="return checkDetails(this);" method ="get">
<p><input type ="text" id = "query" name ="query" />
<input type ="submit" value ="Web Service"/></p>
</form>
</body>
Try this code:
function checkDetails(search)
{
var search = document.getElementById('query');
if(search.value ===''||search.value===null)
{
alert('No search criteria entered');
search.focus();
return false;
}
return true;
}
You wrote documment.
You don't specify in what way it's not working - you get an error, it doesn't validate correctly, you don't get the error alert? One thing I spotted:
query.focus;
Should be
search.focus();
Also you misspelled document as documment
Also try something like this
onSubmit="return checkDetails(this,this.id);"
function checkDetails(search,id)
{
var search = documment.getElementById(id);
if(search.value ==''||search.value==null)
{
alert('No search criteria entered');
query.focus;
return false;
}
}
It will be
search.focus();
instead of
query.focus;
and documment will be document

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