Develop Reference

JavaScript while loop won't increment properly for HTML document [duplicate]

Something that has bugged me for a while and always giving me headaches.
I have an input field with a value in numbers
<input id="base-life" class="base-stats" type="number" name="base-life" value="20" readonly />
I am picking up the value of the input field with
let charlife = document.getElementById('base-life');
I have a number with which i want to increase the value of the base-life input field. This of course changes dynamically based on other stuff but let's say it's 2
let increaseWith = 2;
in an onclick function i want to increase base-life with 2 (base-life + 2) everything it is clicked
function increase() {
charlife.value += increaseWith;
}
Now this only adds 2 to the value of the input field, makes it 202. I know that this happens when one of the numbers are actually strings. Perhaps my charlife. I tried everything and it gets worse. I tried parseInt(charlife.value) - no luck. I tried other methods but it doesn't work. And i only have this problem with input fields. When the element is just a or another simpler html element - it all works easier. Has to do with how JS parses input fields. Can someone shed some light?

let charlife = document.getElementById('base-life');
let increaseWith = 2;
function increase() {
value = parseInt(charlife.value);
value += increaseWith;
charlife.value = value;
}
<input id="base-life" class="base-stats" type="number" name="base-life" value="20" readonly />
<button onclick="increase()">Increase</button>

Here is the working snippet with some custom code that is according to your specifications
<input id="base-life" class="base-stats" type="number" name="base-life" value="20" readonly />
<button class="add" onclick="let increaseWith = 2;document.getElementById('base-life').value = parseInt(document.getElementById('base-life').value)+increaseWith;">add</button>

Use changed values in other page

I have a textfield:
Voornaam: <h3 class="title1">Kevin</h3>
<input type="text" id="myTextField1" />
<input type="submit" id="byBtn" value="Change" onclick="change1()"/><br/>
I can set a value of this using this function:
function change1(){
var myNewTitle = document.getElementById('myTextField1').value;
if( myNewTitle.length==0 ){
alert('Write Some real Text please.');
return;
}
var titles = document.getElementsByClassName('title1');
Array.prototype.forEach.call(titles,title => {
title.innerHTML = myNewTitle;
});
}
Now in my other page, I want to use the value. I know I can for example pass a value from one page to another like this:
<a href='convert.php?var=data'>converteren.</a>
And then for example show it by doing this in the other page:
echo $_GET['var'];
But I cant really seem to figure out how to use the value which I've set using my textfield.
So my goal for now is to display the value I've set using my textfield in the other page using the method I just described.
Basically all I want to happen is for my textfield to change the value inside here aswell:
<a href='convert.php?var=data'>converteren.</a>
So where data is the value, I want it to become what I've put in the textfield.
Could anybody provide me with an example?

I've altered a bit your javascript code to make the link as you want.
To explain the answer, i've added document.getElementById("myLink").href="convert.php?var=" + myNewTitle ; which updates your a href while your function runs and is not empty.
function change1(){
var myNewTitle = document.getElementById('myTextField1').value;
if( myNewTitle.length==0 ){
alert('Write Some real Text please.');
return;
}
document.getElementById("myLink").href="convert.php?var=" + myNewTitle ;
var titles = document.getElementsByClassName('title1');
Array.prototype.forEach.call(titles,title => {
title.innerHTML = myNewTitle;
});
}
<a id="myLink" href='#'>converteren.</a>

Wrap your inputs inside a form element.
In the action attribute, specify the destination url.
In the method attribute, choose between GET and POST.
For example:
<form method="GET" action="convert.php">
<input type="text" id="myTextField1" />
<input type="submit" id="byBtn" value="Change" onclick="change1()"/>
</form>
Clicking the submit button will call "convert.php?myTextField1={value}".

Javascript change hidden field on submit

Hi I am trying to install a merchant facility onto my website and it needs to submit a value $vpc_Amount which is the amount purchased in cents.
What I need to do is multiply the amount entered by the user ($amount) by 100 to get $vpc_Amount.
I tried the following but it isn't working.
<input type="text" ID="A1" name="amount"onkeypress="process1()">
<input type="hidden" id="A2" name="vpc_Amount">
And then the javascript
function process1() {
f1 = document.getElementById("A1").value;
total = f1*1000;
document.getElementById("A2").value = total;
}
What is happening is it is occasionally working but most of the time it doesn't. I know there is something wrong with the script so hence asking here.

Try to use onkeyup function -
<input type="text" id="A1" name="amount" value="" onkeyup="process1();" />
<input type="hidden" id="A2" name="vpc_Amount" />
javascript function -
function process1() {
var f1 = document.getElementById("A1").value;
var total = (f1 * 100);
document.getElementById("A2").value = total;
}

Use Jquery. http://jquery.com/
$(function() {
$('#form_id').submit(function(){
$('#form_id').find('#A2').val('New value');
return true;
});
});

Have you tried to use onkeyup event? It might be so that onkeypress event is triggered before the character is added to text field.
<input type="text" ID="A1" name="amount" onkeyup="process1()">
Also, I would suggest that you try to convert the value of the textfield to integer and add other input handling too. Users might enter any kind of data there and it can crash your javascript code.

This code should work:
document
.getElementById('A1')
.addEventListener('keyup', function (e) {
document.getElementById('A2').value = parseInt(this.value) * 1000;
})
keypress event triggers before value changes in text field and keyup after value has changed.
Basically event trigger in order:
keydown (onkeydown)
keypress (onkeypress)
keyup (onkeyup)
Force value to be integer or you will get NaN in some cases.

I will suggest to use onblur this is the best way if you want to use the build in attribute listener if you don't use jquery. Here is example:
<!DOCTYPE html>
<html>
<body>
Enter your name: <input type="text" id="fname" onblur="myFunction()">
<p>When you leave the input field, a function is triggered which transforms the input text to upper case.</p>
<script>
function myFunction() {
var x = document.getElementById("fname");
x.value = x.value.toUpperCase();
}
</script>
</body>
</html>
And url to the example in w3 school :) http://www.w3schools.com/jsref/event_onblur.asp

First of all, I think you should use onkeypup event and not onkeypress
<input type="text" id="A1" name="amount" onkeyup="process1()" value="" />
<input type="hidden" id="A2" name="vpc_Amount" value="" />
Javascript code -
function process1() {
var f1 = parseFloat(document.getElementById("A1").value);
var total = f1*100; //you said 100 so, I changed to 100
document.getElementById("A2").value = total;
}
jQuery code for the same -
jQuery(document).ready(function($){
$("#A1").keyup(function(){
var total = parseFloat($("#A1").val()) * 100;
$("#A2").val(total);
});
});

Your code can be simplified by making use of the fact that form controls are available as named properties of the form baed on their name. This removes the requirement to add IDs to form controls that must have a name anyway.
Pass a reference to the control in the listener:
<input type="text" name="amount" onkeyup="process1(this)">
<input type="hidden" name="vpc_Amount">
Then use the passed reference to get the form and other controls:
function process1(element) {
element.form.vpc_Amount.value = element.value * 100;
}
You may wish to use the change event instead to save updating the hidden field unnecessarily while the user is typing and also to catch changes that aren't based on key presses (e.g. pasting from the context menu).
You should also do some validation of the values entered so the user doesn't attempt to send the form with invalid values (noting that you must also do validation at the server as client side validation is helpful but utterly unreliable).

How can I count the total number of inputs with values on a page?

I'm hoping for a super simple validation script that matches total inputs on a form to total inputs with values on a form. Can you help explain why the following doesn't work, and suggest a working solution?
Fiddle: http://jsfiddle.net/d7DDu/
Fill out one or more of the inputs and click "submit". I want to see the number of filled out inputs as the result. So far it only shows 0.
HTML:
<input type="text" name="one">
<input type="text" name="two">
<input type="text" name="three">
<textarea name="four"></textarea>
<button id="btn-submit">Submit</button>
<div id="count"></div>
JS:
$('#btn-submit').bind('click', function() {
var filledInputs = $(':input[value]').length;
$('#count').html(filledInputs);
});

[value] refers to the value attribute, which is very different to the value property.
The property is updated as you type, the attribute stays the same. This means you can do elem.value = elem.getAttribute("value") to "reset" a form element, by the way.
Personally, I'd do something like this:
var filledInputs = $(':input').filter(function() {return !!this.value;}).length;

Try this: http://jsfiddle.net/justincook/d7DDu/1/
$('#btn-submit').bind('click', function() {
var x = 0;
$(':input').each(function(){
if(this.value.length > 0){ x++; };
});
$('#count').html(x);
});

Expanding HTML forms using Javascript

I have a simple HTML form that asks a user to input their name, SKU, quantity, and comments. This is for a simple inventory request system.
<html>
<body>
<form id="myForm" method="post">
<input type="submit">
<br>Name: <input type="text" name="form[name]">
<br>SKU: <input type="text" name="form[SKU1]">
<br>Quantity: <input type="text" name="form[quantity1]">
<br>Comment: <input type="text" name="form[comment1]">
</form>
Add item
<script>
var num = 2; //The first option to be added is number 2
function addOption() {
var theForm = document.getElementById("myForm");
var newOption = document.createElement("input");
newOption.name = "form[SKU"+num+"]"; // form[varX]
newOption.type = "text";
theForm.appendChild(newOption); //How can I add a newline here?
optionNumber++;
}
</script>
</body>
</html>
Currently I can only get it working where it will add a single form value. I would like to recreate the entire myForm except for the name field with a single click.

Your post is very old, so presumably you've found an answer by now. However, there are some things amiss with your code.
In the JavaScript code you have
var num = 2;
This is the number that is incremented to keep track of how many "line-items" you will have on the form. In the function addOption(), though, instead of incrementing num you have
optionNumber++;
You never use optionNumber anywhere else. Your code works once, when you add the first item, but since you increment the wrong variable, you are effectively always adding option 2.
Oh, and adding the newline: you need to append a <br> element.