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unable to fetch input from input field

I am not able to get the input, entered by the user, from the input field; please help me out with this.
I am not able to figure out what is wrong here.
var ftemp = document.getElementById("Farenheit").value;
<td>
<input type="number" id="Farenheit">
</td>
when entering value in input field in the web page, input value is not being fetched at all.
console.log-ing the variable just shows a blank line .

This line of code
var ftemp = document.getElementById("Farenheit").value;
gets you the current value of that input at the time that line of code gets executed.
It does not update when the user changes the inputs value.
If you want it to do just that, you need to add an event listener to the input element that executes whenever the input event occurs:
var ftemp;
document.getElementById("Farenheit").addEventListener('input', function() {
ftemp = this.value;
console.log(ftemp);
})
<input type="number" id="Farenheit">

Add an event listener to the input element.
document.querySelector('input').addEventListener('keyup',function() {
console.log(this.value);
});
<input type="number" id="Farenheit" >

Javascript - Display input inside div

So this is probably an easy one, but I'm just not doing it right. My goal is to send the user input from this textbox:
<input type='text' placeholder='Form Name...' id='formNameInput' required>
Into this Div:
<div id="code_output"></div>
I'm trying to make it appear in real time, and so far I used this to try and do so, but it doesn't work:
document.getElementById("code_output").innerHTML += document.getElementById("formNameInput").value;
Why doesn't it show? Does my code need something to trigger the Javascript?

You're close, but the issue is that you're not using an event handler. The script is executing your code once, as soon as possible (before you have the chance to enter anything into the text input). So, you have to add some sort of event listener so that the copying happens at the appropriate time. Something like below:
document.getElementById('formNameInput').addEventListener('keyup', copyToDiv);
function copyToDiv() {
document.getElementById("code_output").innerHTML = document.getElementById("formNameInput").value;
}
<input type='text' placeholder='Form Name...' id='formNameInput' required>
<div id="code_output"></div>

You need to do that whenever the value of formNameInput changes. For that you need an event.
Your code should look like:
document.getElementById("formNameInput").addEventListener('input', function () {
document.getElementById("code_output").innerHTML += this.value;
});

function change() {
document.getElementById("code_output").innerHTML = document.getElementById("formNameInput").value;
}
document.getElementById('formNameInput').onkeyup = change
maybe this is what you are trying?

You need to attach an event listener to your input that executes a function any time an input event occurs on the field:
formNameInput.addEventListener('input', function(e) {
code_output.textContent = e.target.value
})
<input type="text" placeholder="Form Name..." id="formNameInput" required />
<div id="code_output"></div>
Please note that the above code takes advantage of the fact that browsers automatically create a global variable for each element with a unique id attribute value, and this variable has the same name as the value of the id.
If the concept of events is new to you, this might be a good place to get started:
https://developer.mozilla.org/en-US/docs/Learn/JavaScript/Building_blocks/Events

Event listener "change" only works if focus is on object

I'm currently having a little struggle with this. The situation is the following. I have multiple input fields on a page
Input1 and Input2 influence the content of Input3.
Now I wan't an event handler being triggered if content of Input3 changes. I tried:
$('#div-xy').on('change', 'input', function(){console.log('input changed')});
But that only seems to work if the focus is also on Input3 which isn't the case as I'm typing in input2 or input3.
I also tried:
$('#div-xy').bind('DOMSubtreeModified', function(){console.log('CHANGE2')});
which sadly has the same effect. Do you maybe have an idea how to check for changes in Input3? Would appreciate the help.

The change event only triggers on user input, but can be triggered explicitly.
Since you are using jQuery:
$('#input2').change(()=>{
console.log('input 2 is changed');
$('#input3').val('some val');
$('#input3').change()
})
$('#input3').change(()=>{
console.log('input 3 is changed');
})

Try like this:
If you have many of these fields, rather than having a handler be bound to each one, you would get better performance by using a delegated event handler:
HTML:
<div id='parent'>
<input type="text" class="search-field" />
<input type="text" class="search-field" />
<select class="search-field" ><option>1</option><option>2</option></select>
<input type="radio" class="search-field" />
</div>
JS:
$('#parent').on('change', '.search-field', function() {
// validate all search field values
// display search results based on values
// if search results already shown, filter based on $(this).val()
console.log($(this).val());
});

Technically, the change event occurs when the value of an element has been changed BY THE USER. It won't occur on it's own if the value of input3 is changed through jquery or some other code. However you can trigger that in any other jquery function manually and if there is a definition of input.change() then it will be executed.

AngularJs Ng-Keypress event working wrongly?

I am developing an application in Angularjs. I am using ng-keypress event in input type=text. While typing value in text I'm getting wrong values in the keypress function. For example, the first time if I type "1" I am getting undefined. Second time, typing any other value gives the first value
<input ng-model="NodeId_1" type="text" ng-keypress="getValue()"/>
var angularapp = angular.module('nameapp', []);
angularapp.controller('NameCtrl', function ($scope) {
$scope.getValue = function () {
alert($scope.NodeId_1);//Here first time undefined is coming and second what ever we enter first value will come
}
}
)

You'll want to use ng-keyup instead.
ng-keypress happens as the key is pressed, and BEFORE the value populates the input. This is why you're not getting any value on the first keypress, but on subsequent presses you will.
Use ng-keyup and your problem is solved, as it happens once the value has already populated the input.
<input ng-model="NodeId_1" type="text" ng-keyup="getValue()" />
ng-keypress is working as intended, but it is not the directive applicable to your requirements.
Working plunkr: http://plnkr.co/edit/OHWDZo68siDlcrXnLyzJ?p=preview

The keypress event is fired when a key is pressed down and that key
normally produces a character value (use input instead).
https://developer.mozilla.org/en-US/docs/Web/Events/keypress
So neither the input field value nor the scope value(apply/digest loop etc.) will reflect the expected input value.
Solution is depending on your requirements. Here are some:
1) Use another event on the inputfield: change, keyup, ...
2) Use the $event object in your listener method:
<input ng-model="NodeId_1" type="text" ng-keypress="getValue($event)"/>
$scope.getValue = function (event) {
console.log(event)
}
3) Create a watcher for your NodeId_1 value within your scope:
$scope.$watch('NodeId_1', function(newVal) {
...
});

The watcher function work for me, I attached my example
$scope.$watch('itemm.montoAmodificar', function (newValue) {
$scope.fnActualizarNuevoSaldoDependencia(parseFloat(newValue));
});
The html code is the following
<input ng-model="itemm.montoAmodificar" my-focus class="form-control" type="text" placeholder="Ingrese el monto" ng-keypress="fnActualizarNuevoSaldoDependencia($event);" />

html <input type="text" /> onchange event not working

I am trying to do some experiment. What I want to happen is that everytime the user types in something in the textbox, it will be displayed in a dialog box. I used the onchange event property to make it happen but it doesn't work. I still need to press the submit button to make it work. I read about AJAX and I am thinking to learn about this. Do I still need AJAX to make it work or is simple JavaScript enough? Please help.
index.php
<script type="text/javascript" src="javascript.js"> </script>
<form action="index.php" method="get">
Integer 1: <input type="text" id="num1" name="num1" onchange="checkInput('num1');" /> <br />
Integer 2: <input type="text" id="num2" name="num2" onchange="checkInput('num2');" /> <br />
<input type="submit" value="Compute" />
</form>
javascript.js
function checkInput(textbox) {
var textInput = document.getElementById(textbox).value;
alert(textInput);
}

onchange is only triggered when the control is blurred. Try onkeypress instead.

Use .on('input'... to monitor every change to an input (paste, keyup, etc) from jQuery 1.7 and above.
For static and dynamic inputs:
$(document).on('input', '.my-class', function(){
alert('Input changed');
});
For static inputs only:
$('.my-class').on('input', function(){
alert('Input changed');
});
JSFiddle with static/dynamic example: https://jsfiddle.net/op0zqrgy/7/

HTML5 defines an oninput event to catch all direct changes. it works for me.

Checking for keystrokes is only a partial solution, because it's possible to change the contents of an input field using mouse clicks. If you right-click into a text field you'll have cut and paste options that you can use to change the value without making a keystroke. Likewise, if autocomplete is enabled then you can left-click into a field and get a dropdown of previously entered text, and you can select from among your choices using a mouse click. Keystroke trapping will not detect either of these types of changes.
Sadly, there is no "onchange" event that reports changes immediately, at least as far as I know. But there is a solution that works for all cases: set up a timing event using setInterval().
Let's say that your input field has an id and name of "city":
<input type="text" name="city" id="city" />
Have a global variable named "city":
var city = "";
Add this to your page initialization:
setInterval(lookForCityChange, 100);
Then define a lookForCityChange() function:
function lookForCityChange()
{
var newCity = document.getElementById("city").value;
if (newCity != city) {
city = newCity;
doSomething(city); // do whatever you need to do
}
}
In this example, the value of "city" is checked every 100 milliseconds, which you can adjust according to your needs. If you like, use an anonymous function instead of defining lookForCityChange(). Be aware that your code or even the browser might provide an initial value for the input field so you might be notified of a "change" before the user does anything; adjust your code as necessary.
If the idea of a timing event going off every tenth of a second seems ungainly, you can initiate the timer when the input field receives the focus and terminate it (with clearInterval()) upon a blur. I don't think it's possible to change the value of an input field without its receiving the focus, so turning the timer on and off in this fashion should be safe.

onchange only occurs when the change to the input element is committed by the user, most of the time this is when the element loses focus.
if you want your function to fire everytime the element value changes you should use the oninput event - this is better than the key up/down events as the value can be changed with the user's mouse ie pasted in, or auto-fill etc
Read more about the change event here
Read more about the input event here

use following events instead of "onchange"
- onkeyup(event)
- onkeydown(event)
- onkeypress(event)

Firstly, what 'doesn't work'? Do you not see the alert?
Also, Your code could be simplified to this
<input type="text" id="num1" name="num1" onkeydown="checkInput(this);" /> <br />
function checkInput(obj) {
alert(obj.value);
}

I encountered issues where Safari wasn't firing "onchange" events on a text input field. I used a jQuery 1.7.2 "change" event and it didn't work either. I ended up using ZURB's textchange event. It works with mouseevents and can fire without leaving the field:
http://www.zurb.com/playground/jquery-text-change-custom-event
$('.inputClassToBind').bind('textchange', function (event, previousText) {
alert($(this).attr('id'));
});

A couple of comments that IMO are important:
input elements not not emitting 'change' event until USER action ENTER or blur await IS the correct behavior.
The event you want to use is "input" ("oninput"). Here is well demonstrated the different between the two: https://javascript.info/events-change-input
The two events signal two different user gestures/moments ("input" event means user is writing or navigating a select list options, but still didn't confirm the change. "change" means user did changed the value (with an enter or blur our)
Listening for key events like many here recommended is a bad practice in this case. (like people modifying the default behavior of ENTER on inputs)...
jQuery has nothing to do with this. This is all in HTML standard.
If you have problems understanding WHY this is the correct behavior, perhaps is helpful, as experiment, use your text editor or browser without a mouse/pad, just a keyboard.
My two cents.

onkeyup worked for me. onkeypress doesn't trigger when pressing back space.

It is better to use onchange(event) with <select>.
With <input> you can use below event:
- onkeyup(event)
- onkeydown(event)
- onkeypress(event)

when we use onchange while you are typing in input field – there’s no event. But when you move the focus somewhere else, for instance, click on a button – there will be a change event
you can use oninput
The oninput event triggers every time after a value is modified by the user.Unlike keyboard events, it triggers on any value change, even those that does not involve keyboard actions: pasting with a mouse or using speech recognition to dictate the text.
<input type="text" id="input"> oninput: <span id="result"></span>
<script>
input.oninput = function() {
console.log(input.value);
};
</script>
If we want to handle every modification of an <input> then this event is the best choice.

I have been facing the same issue until I figured out how to do it. You can utilize a React hook, useEffect, to write a JS function that will trigger after React rendering.
useEffect(()=>{
document.title='fix onChange with onkeyup';
const box = document.getElementById('changeBox');
box.onkeyup = function () {
console.log(box.value);
}
},[]);
Note onchange is not fired when the value of an input is changed. It is only changed when the input’s value is changed and then the input is blurred. What you’ll need to do is capture the keypress event when fired in the given input and that's why we have used onkeyup menthod.
In the functional component where you have the <Input/> for the <form/>write this
<form onSubmit={handleLogin} method='POST'>
<input
aria-label= 'Enter Email Address'
type='text'
placeholder='Email Address'
className='text-sm text-gray-base w-full mr-3 py-5 px-4 h-2 border border-gray-primary rounded mb-2'
id='changeBox'
/>
</form>
Resulting Image :
Console Image

try onpropertychange.
it only works for IE.