I am new to HTML and JavaScript. I just made a simple page to add two numbers. The output that I am getting is correct but when I click the sum button the sum is there for a fraction of second and then again the page reloads itself.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>First</title>
<script>
function get_sum() {
let num_a = parseInt(document.getElementById('first').value);
let num_b = parseInt(document.getElementById('second').value);
document.getElementById('sum').innerText = (num_a + num_b).toString(10);
}
</script>
</head>
<body>
<form id="form" onsubmit="return get_sum()">
<label>First Number: <input type="text" id="first" placeholder="Enter a number" required></label>
<br>
<label>Second Number: <input type="text" id="second" placeholder="Enter a number" required></label>
<button type="submit">Sum </button>
</form>
<h1 id="sum"></h1>
</body>
</html>
You need to pass the event and add event.preventDefault(); at the beginning of the function to prevent page from reloading since it's a submit button:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>First</title>
<script>
function get_sum(event) {
event.preventDefault();
let num_a = parseInt(document.getElementById('first').value);
let num_b = parseInt(document.getElementById('second').value);
document.getElementById('sum').innerText = (num_a + num_b).toString(10);
}
</script>
</head>
<body>
<form id="form" onsubmit="return get_sum(event)">
<label>First Number: <input type="text" id="first" placeholder="Enter a number" required></label>
<br>
<label>Second Number: <input type="text" id="second" placeholder="Enter a number" required></label>
<button type="submit">Sum </button>
</form>
<h1 id="sum"></h1>
</body>
</html>
The onsubmit must return false to prevent browser from submitting it to server.
Like this
<form id="form" onsubmit="get_sum(); return false;">
You can add an event listener to handle the click after you change the type to "button". Or you can stop the event from propagating to the actual "submit" action. OR, do both to prevent the submit of the form.
Why both? A form can also be submitted by hitting "return/enter" or via script.
This is perhaps a bit of overkill but shows how to handle the events.
function get_sum(event) {
event.preventDefault();
let num_a = parseInt(document.getElementById('first').value);
let num_b = parseInt(document.getElementById('second').value);
document.getElementById('sum').innerText = (num_a + num_b).toString(10);
}
const sumButton = document.getElementById('sum-click');
sumButton.addEventListener("click", get_sum, false);
const form = document.getElementById('form');
form.addEventListener('submit', get_sum);
<form id="form">
<label>First Number: <input type="text" id="first" placeholder="Enter a number" required></label>
<br>
<label>Second Number: <input type="text" id="second" placeholder="Enter a number" required></label>
<button id="sum-values" type="submit">Sum </button>
<button id="sum-click" type="button">Sum (Not submit)</button>
</form>
<h1 id="sum"></h1>
Related
I'm pretty new to JavaScript and am creating a simple page to output the form values. But there's seem to be a problem that it is not showing.
<html>
<head>
<title>Return first and last name from a form - w3resource</title>
</head>
<body>
<form id="form1" onsubmit="form()">
First name: <input type="text" name="fname" value="David"><br>
Last name: <input type="text" name="lname" value="Beckham"><br>
<input type="submit" value="Submit">
</form>
<p id="firstname"></p>
<script>
function form() {
var x = document.getElementById("form1").elements[0].value;
document.getElementById("firstname").innerHTML = x;
}
</script>
</body>
</html>
I can't seem to find any problems, the console was fine with the code.
You have to stop the form from submitting.
<html>
<head>
<title>Return first and last name from a form - w3resource</title>
</head>
<body>
<form id="form1" onsubmit="return form()">
First name: <input type="text" name="fname" value="David"><br>
Last name: <input type="text" name="lname" value="Beckham"><br>
<input type="submit" value="Submit">
</form>
<p id="firstname"></p>
<script>
function form() {
var x = document.getElementById("form1").elements[0].value;
document.getElementById("firstname").innerHTML = x;
return false;
}
</script>
</body>
</html>
Use an event listener to handle the submit and preventDefault() for stopping the submission. Following code is tested and working.
<html>
<head>
<title>Return first and last name from a form - w3resource</title>
</head>
<body>
<form id="form1">
First name: <input type="text" name="fname" value="David"><br>
Last name: <input type="text" name="lname" value="Beckham"><br>
<input type="submit" value="Submit">
</form>
<p id="firstname"></p>
<script>
document.getElementById("form1").addEventListener("submit", form);
function form(e) {
e.preventDefault();
var x = document.getElementById("form1").elements[0].value;
document.getElementById("firstname").innerHTML = x;
}
</script>
</body>
</html>
<script src="script.js"></script>
</body>
</html>
I am trying to create a simple form using Javascript, but I am facing an issue while trying to display somethings on the console. The issue here is that whenever I click on the submit button, Nothing is displayed on the console despite giving the command e.preventdefault(). At present I want the text Hello to be displayed on console when it satisfies the condition, but even though the condition is satisfied, nothing is displayed.
Herewith attaching the Javascript and HTML code for the same
const passlength = 10;
const firstname = document.getElementById("firstname");
const lastname = document.getElementById("lastname");
const emailid = document.getElementById("emailid");
const password = document.getElementById("pass");
const confirmpassword = document.getElementById("passconfirm");
const phonenumber = document.getElementById("phno");
const form = document.querySelector(".mainform");
function testfunc() {
console.log(type(emailid));
}
function checkpass(pass) {
if (pass>=passlength) {
console.log("Hello");
}
else{
console.log("Out");
}
}
form.addEventListener('submit',function(e){
e.preventDefault();
checkpass(password);
})
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Register with us</title>
</head>
<body>
<div class="mainform">
<form>
<label for="firstname">First name:</label>
<input type="text" id="firstname" name="firstname"><br>
<label for="lastname">Last name:</label>
<input type="text" id="lastname" name="lastname"><br>
<label for="emailid">Email ID:</label>
<input type="email" id="emailid" name="emailid"><br>
<label for="pass">Enter password:</label>
<input type="password" id="pass" name="pass"> <br>
<label for="passconfirm">Confirm password:</label>
<input type="password" id="passconfirm" name="passconfirm"> <br>
<label for="phno">Phone number:</label>
<input type="number" id="phno" name="phno">
<br> <br>
<input type="submit" value="Submit" id="submit">
</form>
</div>
</body>
</html>
The problem is in your If statement. You are comparing a number with an HTML element. You still need these two.
.value returns the value of the html element
https://www.w3schools.com/jsref/prop_text_value.asp
.length returns the length of a string
https://developer.mozilla.org/de/docs/Web/JavaScript/Reference/Global_Objects/String/length
This is how you compare two numbers, as you intended.
So your new IF condition must be:
(pass.value.length>=passlength)
I've written a validator for my HTML although I'm not sure where I'm going wrong.
What I'm trying to do below is determine if there is any text in the "First Name" box altogether. There is underlying css to the code but I believe my issue is surrounding my onsubmit and validate function as nothing in the javascript seems to be running once I click the submit button.
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>NewPatientForm</title>
<link rel="stylesheet" type="text/css" href="NewPatient.css">
<script>
function validate() {
var invalid = false;
if(!document.Firstname.value.length) {
invalid = true;
}
if(invalid) {
document.getElementById("form-error").style.display = "inline-block";
return false; //to make the text appear
}
return true;
}
</script>
</head>
<body>
<form id="NewPatientForm" method="post" action="#" onsubmit="return validate();">
<div class="form-element">
<p id="form-error">All fields are required</p>
</div>
<div>
<label for="Firstname">First Name
<input type="text" name="Firstname" placeholder="First Name" id="Firstname">
</label>
</div>
<div>
<input type="submit" name="submit-button" value="Submit">
</div>
</form>
</body>
</html>
Looks like the culprit was your attempt to access Firstname on the document object.
I replaced it with the more standard document.getElementById() method and its working.
Some reading on this: Do DOM tree elements with ids become global variables?
function validate() {
var invalid = false;
if(!document.getElementById('Firstname').value.length) {
invalid = true;
}
if(invalid) {
document.getElementById("form-error").style.display = "inline-block";
return false;
}
return true;
}
#form-error {
display: none;
}
<form id="NewPatientForm" method="post" action="#" onsubmit="return validate()">
<div class="form-element">
<p id="form-error">All fields are required</p>
</div>
<div>
<label for="Firstname">First Name
<input type="text" name="Firstname" placeholder="First Name" id="Firstname">
</label>
</div>
<div>
<input type="submit" name="submit-button" value="Submit">
</div>
</form>
There are a couple of typos, and I'll suggest something else as well. First, a fix or three in the code:
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>NewPatientForm</title>
<script>
function validate() {
const invalid = document.getElementById("Firstname").value.length == 0;
if(invalid) {
document.getElementById("form-error").style.display = "inline-block";
return false; //to make the text appear
}
return true;
}
</script>
</head>
<body>
<form id="NewPatientForm" method="post" action="#" onsubmit="return validate();">
<div class="form-element">
<p id="form-error">All fields are required</p>
</div>
<div>
<label for="Firstname">First Name
<input type="text" name="Firstname" placeholder="First Name" id="Firstname">
</label>
</div>
<div>
<input type="submit" name="submit-button" value="Submit">
</div>
</form>
</body>
</html>
My suggestion is that you also look into built-in HTML form validation attributes. I'm thinking you're reinventing the wheel for things like requiring a non-empty Firstname. Why not this instead of JavaScript?
<input type="text" name="Firstname" id="Firstname" placeholder="First Name" required />
And many others, like minlength="", min="", step="", etc.
Plus there's still a JavaScript hook into the validation system with .checkValidity() so you can let the built-in validation do the heavy lifting, and then throw in more of your own custom aspects too.
I need to do a simple homework where you enter two integers in two text fields of a form and then you compute the sum and you print it in a "text field (not editable)". My program seems to work but it prints the right output and immediately reload the page. I want the page to remain with the printed output if the user does not click again on "submit" button
Here is my code HTML & JS :
function updateExpr() {
var x1 = document.getElementById("n1").value;
var x2 = document.getElementById("n2").value;
var sum = +x1 + +x2;
document.getElementById("sum").innerHTML = +x1 + +x2;
}
<!DOCTYPE html>
<html>
<head>
<title>Number in a form</title>
<link href="mystyle.css" rel="stylesheet" type="text/css"/>
<script type="text/javascript" src="function.js">
</script>
</head>
<body>
<div id="mainDiv">
<H3>Insert two positive numbers</H3>
<form>
First number:<br>
<input id="n1" type="text" name="firstname"><br>
Second number:<br>
<input id="n2" type="text" name="lastname">
<BR>
<input type="submit" value="Submit" onClick="updateExpr()"/><BR><BR>
</form>
The sum is:<br>
<output id="sum" name="x" for="a b"></output>
</div>
<noscript>
Sorry: Your browser does not support or has disabled javascript
</noscript>
</body>
</html>
When form is submited, the page will be reloaded. To prevent this you should change input type attribute from submit to button.
<input type="submit" value="Submit" onClick="updateExpr()"/>
to
<input type="button" value="Submit" onClick="updateExpr()"/>
You can simply avoid server call by changing your form tag
<form onSubmit="return false">
You dont really need a form to do something like this.
Forms send values to the backend, e.g. a server.
You only want to manipulate some front-end elements like a container to have some new text inside it.
a <form> tag typically sends you to some URI with some aprameters,
this is done by the actions attribute.
<form action="addnames.php">
for example would call the addnames.php script on your server...
You dont need a server tho..look below:
function updateExpr() {
var x1 = document.getElementById("n1").value;
var x2 = document.getElementById("n2").value;
var sum =x1 +x2;
document.getElementById("sum").innerHTML = sum;
}
<h2>HTML Forms</h2>
First name:<br>
<input id="n1" type="text" name="firstname" value="Mickey">
<br>
Last name:<br>
<input id="n2" type="text" name="lastname" value="Mouse">
<br><br>
<button type="submit" onclick="updateExpr()">Submit</button>
<div id="sum">
</div>
<script>
</script>
I would recommand you to add onSubmit method to the form instead of onclick to the input.
Also you better add a return : false to your function and add onsubmit="return updateExpr()".
function updateExpr() {
var x1 = document.getElementById("n1").value;
var x2 = document.getElementById("n2").value;
var sum = +x1 + +x2;
document.getElementById("sum").innerHTML = +x1 + +x2;
return false;
}
<!DOCTYPE html>
<html>
<head>
<title>Number in a form</title>
<link href="mystyle.css" rel="stylesheet" type="text/css"/>
<script type="text/javascript" src="function.js">
</script>
</head>
<body>
<div id="mainDiv">
<H3>Insert two positive numbers</H3>
<form onsubmit="return updateExpr()">
First number:<br>
<input id="n1" type="text" name="firstname"><br>
Second number:<br>
<input id="n2" type="text" name="lastname">
<BR>
<input type="submit" value="Submit" onClick="updateExpr()"/><BR><BR>
</form>
The sum is:<br>
<output id="sum" name="x" for="a b"></output>
</div>
<noscript>
Sorry: Your browser does not support or has disabled javascript
</noscript>
</body>
Another way of doing this would have been to add a button outside of the form linked to the function by onclick event
juste add preventDefault(), like this
function updateExpr(e) {
e.preventDefault();
var x1 = document.getElementById("n1").value;
var x2 = document.getElementById("n2").value;
var sum = +x1 + +x2;
document.getElementById("sum").innerHTML = +x1 + +x2;
}
Quick question. I am starting learn on local storage HTML5. How can I get value from a form and display that value on another HTML form page?
For example, I have two forms here.
If I fill on form 1 and click submit button, and the value will display on form 2 in readable only.
I tried below:
HTML Form 1:
<html>
<head>
<title>Save Value</title>
<script type="text/javascript">
function saveVal() {
var inputFirst = document.getElementById("name").value;
localStorage.setItem("name", inputFirst);
inputFirst = localStorage.getItem("name");
}
</script>
</head>
<body>
<form action="display.html" method="get">
<label>
First Name:
<input name="name" size="20" maxlength="25" type="text" id="name" />
</label>
<input type="submit" value="submit" onclick="saveVal()"/>
</form>
</body>
</html>
HTML Form 2:
<html>
<head>
<title>Display</title>
<script type="text/javascript">
function result() {
var storedVal = document.getElementById("name");
storedVal.value = localStorage.getItem("name");
}
</script>
</head>
<body>
<form action="#">
<label>
First Name:
<input name="name" size="20" maxlength="25" type="text" id="name" readonly="readonly" />
</label>
</form>
</body>
</html>
In display.html you didn't call function result(),
try this,
<html>
<head>
<title>Display</title>
</head>
<body>
<form action="#">
<label>
First Name:
<input name="name" size="20" maxlength="25" type="text" id="name" readonly="readonly" />
</label>
<script type="text/javascript">
var storedVal = document.getElementById("name");
storedVal.value = localStorage.getItem("name");
</script>
</form>
</body>
</html>