JavaScript empty field validation does not work - javascript

So, I have a number textbox and I want to validate it using JavaScript. If the user has not input any number, it will prompt him/her to enter one. My codes below:
<input type="number" autofocus id="lol"/>
<input type="button" onClick="validate()" value="Input"/>
<script>
function validate() {
var numfield = document.getElementById("lol").value;
if ( numfield == "") {
document.write("Missing number!");
}
</script>
What is wrong?

You have missed a } at the end of the script. With that fixed, it works normally.

Try to use length property.
if ( numfield.length > 0) {
...
}

Related

How To Validate Form Field Using Javascript

I am trying to validate my form phone field to prevent users from entering the same numbers in my javascript.
If the number provided by the user matches with the same numbers in my javascript, They will get a warning and the form would not submit.
However, I noticed that my code below shows the warning whether the numbers match or not.
I need corrections to know what I am doing wrong. Thanks.
Code below;
$('.validate').hide();
$('body').on('blur', '#phone', function() {
$('.validate').hide();
isphone($(this).val());
});
function isphone(phone) {
if (phone === "1234" || phone === "23456"){
$(".validate").show();
} else {
$(".validate").hide();
}
}
<script src="https://code.jquery.com/jquery-1.12.4.js"></script>
<form action='' method='POST' id="submitForm" >
<input type="phone" name='phone' required='' id="phone" placeholder="0000-000-0000"/>
<div class="validate"><span style="color: red;"><b>Please enter a valid phone!</b></span></div>
<button href='/' type='submit' id="submitForm">Process</button>
</form>
I believe this should work.
I move the changes for hiding and showing $('.validate') to the isphone function, and removed that done variable that wasn't doing anything useful (used if...else instead).
Also, don't use document.getElementById if you're already using JQuery.
$('.validate').hide();
$('body').on('blur', '#phone', function() {
$('.validate').hide();
isphone($(this).val());
});
function isphone(phone) {
if (phone === "1234" || phone === "23456"){
$(".validate").hide();
} else {
$(".validate").show();
}
}

Javascript form validation return false error

I'm trying to do a form and while the alert is popping up it is still submitting. How do I get it to stop submitting??
function validate() {
var first = document.register.first.value;
if (first == "") {
alert("please enter your name");
first.focus();
return false;
}
return (true);
}
<body>
<form name="register" action="testform.php" onsubmit="return(validate());">
<input type="text" name="first" />
<button type="submit" />Submit
</form>
</body>
You added the parenthesis on return() then return(validate()) which we use () when calling the function so it might be considering return a custom function which returns undefined and when returned the undefined it ignores and continue the execution.
How ever the validate is called but it's response is not returned to the form.
Fixed version:
<head>
<script>
function validate(e) {
var first = document.register.first.value;
console.log(document.register.first)
if( first == "" ) {
alert( "please enter your name" ) ;
return false;
}
return(true);
}
</script>
</head>
<body>
<form name="register" action="testform.php" onsubmit="return validate()">
<input type="text" name="first" />
<button type="submit" >sbmit</button>
</form>
</body>
You are better of using the required attribute on the front end of things. It will 'force' the user to input text into the input field before it is able to submit. Please note that I put quotation marks around the word 'force', because one can just edit the HTML and circumvent the HTML required attribute. Therefore make absolutely sure that you are validating user input on the PHP side as well.
Many tutorials and examples exist for PHP Form Validation, such as this one from W3Schools and this one from Medium.
<form name="register" action="testform.php">
<input type="text" name="first" required/>
<input type="submit" value="Submit"/>
</form>
You have several bugs in your code.
<button> element is not self-closing
you are calling focus on value of the input instead of the input element which throws exception
function validate() {
var input = document.register.first;
var text = input.value;
if( text == "" ) {
alert( "please enter your name" ) ;
input.focus();
return false;
}
return true;
}
I think the issue is with the button's type="submit". Try changing it to type="button", with an onclick function that submits your form if validate() returns true.
edit: Arjan makes a good point, and you should use required. But this answers why the form was submitting.

jQuery Click Function, input value length and pattern

I have a problem, that I'm struggling with since 2 days.
I have a webpage that asks for the phone number, and I'm trying to make a "validator" for the phone number into the input tab, but it seems that I cannot figure out how to check the minlength for the input tab, neither how to accept only numerical characters. Here's the code:
$("#start").click(function(){ // click func
if ($.trim($('#phonenr').val()) == ''){
$("#error").show();
I tried adding:
if ($.trim($('#phonenr').val()) == '') && ($.trim($('#phonenr').val().length) < 15)
But it just won't work.
Any help would be appreciated. Also please tell me how can I make it allow only numbers?
Thank you!
Final code, with help of #Saumya Rastogi.
$("#start").click(function(){
var reg = /^\d+$/;
var input_str = $('#phonenr').val();
chopped_str = input_str.substring(0, input_str.length - 1);
if(!reg.test(input_str)) {
$("#error").show();
return;
}
if(($.trim(input_str) == '') || ($.trim(input_str).length < 15)) {
$("#error").show();
} else {
You can make your validation work.
You can use test (Regex Match Test) for accepting only digits in the input text. Just use javascript's substring to chop off the entered non-digit character like this:
$(function() {
$('#btn').on('click',function(e) {
var reg = /^\d+$/; // <------ regex for validatin the input should only be digits
var input_str = $('#phonenr').val();
chopped_str = input_str.substring(0, input_str.length - 1);
if(!reg.test(input_str)) {
$('label.error').show();
return;
}
if(($.trim(input_str) == '') || ($.trim(input_str).length < 15)) {
$('label.error').show();
} else {
$('label.error').hide();
}
});
})
label.error {
display: none;
color: red;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input id="phonenr" type="text" value=""><br>
<label class='error'>Invalid Number</label>
<br><br>
<button id="btn">Click to Validate</button>
Hope this helps!
If you are using HTML5, then you can make use of the new number input type available
<input type="number" name="phone" min="10" max="10">
You can also use the pattern attribute to restrict the input to a specific Regular expression.
If you are looking for the simplest way to check input against a pattern and display a message based on validity, then using regular expressions is what you want:
// Wait until the DOM has been fully parsed
window.addEventListener("DOMContentLoaded", function(){
// Get DOM references:
var theForm = document.querySelector("#frmTest");
var thePhone = document.querySelector("#txtPhone");
var btnSubmit = document.querySelector("#btnSubmit");
// Hook into desired events. Here, we'll validate as text is inputted
// into the text field, when the submit button is clicked and when the
// form is submitted
theForm.addEventListener("submit", validate);
btnSubmit.addEventListener("click", validate);
thePhone.addEventListener("input", validate);
// The simple validation function
function validate(evt){
var errorMessage = "Not a valid phone number!";
// Just check the input against a regular expression
// This one expects 10 digits in a row.
// If the pattern is matched the form is allowed to submit,
// if not, the error message appears and the form doesn't submit.
!thePhone.value.match(/\d{3}\d{3}\d{4}/) ?
thePhone.nextElementSibling.textContent = errorMessage : thePhone.nextElementSibling.textContent = "";
evt.preventDefault();
}
});
span {
background: #ff0;
}
<form id="frmTest" action="#" method="post">
<input id="txtPhone" name="txtPhone"><span></span>
<br>
<input type="submit" id="btnSubmit">
</form>
Or, you can take more control of the process and use the pattern HTML5 attribute with a regular expression to validate the entry. Length and digits are checked simultaneously.
Then you can implement your own custom error message via the HTML5 Validation API with the setCustomValidity() method.
<form id="frmTest" action="#" method="post">
<input type="tel" id="txtPhone" name="txtPhone" maxlength="20"
placeholder="555-555-5555" title="555-555-5555"
pattern="\d{3}-\d{3}-\d{4}" required>
<input type="submit" id="btnSubmit">
</form>
Stack Overflow's code snippet environment doesn't play well with forms, but a working Fiddle can be seen here.

JavaScript string is not a function

When working on a page whenever I call on my second function, validateNumber(), I get a "typeError: String is not a function" message can anyone explain to me why this message is occuring? My code is as follows:
< script type = "text/javascript" >
/* <![CDATA[ */
function validateLetter(dataEntry) {
try {
var textInput = dataEntry.value;
var replacedInput = textInput.replace(/[^A-Za-z]/g);
if (textInput != replacedInput)
throw "You can only enter letters into this field.";
dataEntry.value = replacedInput;
} catch (textInputError) {
window.alert(textInputError)
return false;
}
return true;
}
function validateNumber(dataEntry) {
try {
var textInput = dataEntry.value;
var replacedInput = textInput(/[^0-9]/g);
if (textInput != replacedInput)
throw "You can only enter numbers into this field.";
} catch (numberInputError) {
window.alert(numberInputError)
return false;
}
return true;
}
function validateInput(dataEntry) {
if (navigator.appName == "Microsoft INternet Explorer")
var enteredKey = dataEntry.keyCode;
else if (navigator.appName == "Netscape")
var eneteredKey = dataEntry.charCode;
}
/* ]] */
< /script>
<form action="validateTheCharacters" enctype="application/x-www-form-urlencoded" name="dataEntry">
<p>Enter your mother's maiden name:
<input type="text" id="letter1" name="letter1" onkeypress="validateLetter(this)">
</p>
<p>Enter the city you were born in:
<input type="text" id="letter2" name="letter2" onkeypress="validateLetter(this)">
</p>
<p>Enter the street you grew up on:
<input type="text" id="letter3" name="letter3" onkeypress="validateLetter(this)">
</p>
<p>Enter your phone number:
<input type="text" id="number1" name="number1" onkeypress="validateNumber(this)">
</p>
<p>Enter the year you were born:
<input type="text" id="number2" name="number2" onkeypress="validateNumber(this)">
</p>
<p>Enter the number of siblings you have:
<input type="text" id="number3" name="number3" onkeypress="validateNumber(this)">
</p>
<p>
<button type="reset" value="Reset Form">Reset Form</button>
</p>
</form>
I am almost certain this is the problem:
var textInput = dataEntry.value;
var replacedInput = textInput(/[^0-9]/g);
if textInput is a string you cannot pass parameters to it as if it were a function, instead:
var replacedInput = textInput.replace(/[^0-9]/g, ""); // dependening in what you are trying to achieve of course
var replacedInput = textInput(/[^0-9]/g);
That's not how you do search and replace in Javascript.
It's not quite clear what you intended here, but if you wanted to remove non-digits from the string, you'd do that using String.replace():
var replacedInput = textInput.replace(/[^0-9]/g, "");
That being said, an easier way of accomplishing this check would be to skip the replacement entirely and just use String.match() instead:
var textInput = dataEntry.value;
if (textInput.match(/[^0-9]/))
throw "You can only enter letters into this field.";
dataEntry.value = textInput;
You might consider isolating functionality so that functions like validateLetter simply validate that the string they are passed contains only letters, then have the caller function work out what to do if the return value is true or not.
In that case, you end up with very much simpler functions:
function validateLetters(s) {
return /^[a-z]+$/i.test(s);
}
function validateNumbers(s) {
return /^\d+$/.test(s);
}
To validate an input, you can add a class to say what type of validation it should have, e.g.
<input name="letter3" class="letter" onkeypress="validateLetter(this)">
Then the validateInput function can determine which validation function to call based on the class:
function validateInput(element) {
var value = element.value;
// If has class letter, validate is only letters
if (/(\s|^)letter(\s|$)/i.test(element.className)) {
// validate only if there is a value other than empty string
if (!validateLetters(value) && value != '') {
alert('Please enter only letters');
}
}
// If has class number, validate is only numbers
if (/(\s|^)number(\s|$)/i.test(element.className)) {
// validate only if there is a value other than empty string
if (!validateNumbers(element.value) && value != '') {
alert('Please enter only numbers');
}
}
}
Note that keypress is not a good event to use for validation as data can be entered without pressing any keys (e.g. paste from the context menu or drag and drop). Also, the listener doesn't see the value resulting from the keypress, it sees the previous value.
You really only need to perform validation when the form is submitted. Until then, why do you care what the values are? Allow the user to make mistakes and fix them themselves without being pestered by alerts (onscreen hints are really useful). Spend some time using your forms to enhance their usability (I realise this is probably not a production form, but names can have characters other than the letters a to z, e.g. von Braun and O'Reilly).
Lastly, form controls rarely need an ID, the name is usually sufficient to identify them if required (and they must have a name to be successful, so most have a name already). A bit of play HTML from the OP:
<form>
<p>Enter your mother's maiden name:
<input name="letter1" class="letter" onkeypress="validateInput(this)">
</p>
<p>Enter the number of siblings you have:
<input name="number3" class="number" onkeypress="validateInput(this)">
</p>
<p>
<input type="reset">
</p>
</form>

Validating phone number with JavaScript

I have a form with three elements. I want to validate the phone number when the user enters it. If the user moves to the next element and phone number contains and characters which is not numbers I want to display an alertbox.
I have written some code but am completely stumped. The problem I am having with my function is, that even if I enter only numbers into the phone number element I still get the alert box displayed. My code looks like this:
<script type="text/javascript">
function validateForm()
{
checkNr= isNaN(document.forms[0].elements[1])
if(checkNr == true)
{
window.alert("You can only enter numbers. Please try again")
}
}
</script>
<form>
<strong>FULLNAME: </strong><input type="text" / id="name"><br />
<strong>PHONE NR: </strong><input type="text" id="phone" onblur="validateForm()" />
<strong>NATIONALITY</strong><input type="text" id="nat" /><br />
<input type="button" id="subButton" onclick="calc()" value="Submit" />
</form>
Thank you in advance for all your answers and help.
Change
document.forms[0].elements[1]
to
document.forms[0].elements[1].value
You were testing the element itself, not the element's value.
jsFiddle example
BTW, if someone enters a phone number with a dash or parenthesis (e.g. (555) 123-4567) what do you expect to happen?
Here you will find many exemple to achieve your goal :
for example if you can use only number :
function phonenumber(inputtxt)
{
var phoneno = /^\d{10}$/;
if((inputtxt.value.match(phoneno))
{
return true;
}
else
{
alert("message");
return false;
}
}
You should do it with a regular expression. See here:
A comprehensive regex for phone number validation
Validate phone number with JavaScript

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