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can I remove a line in my HTML code with javascript?

I have this code:
<div class="input">
<input type="number" id="myID" oninput="myFunction()">
<div>
<h3>MY TEXT</h3>
</div>
</div>
and I want to make a javascript code to remove the div below the input field whenever I write anything in the input
..........
I tried this code:
function myFunction(){
var field = document.getElementById("myID");
var num = field.value;
var parent = field.parentNode;
parent.innerHTML = field.outerHTML;
field.value = num;
}
but it have a problem each time I make an input, I have to re-click inside the input to make it active again
check out the code here

You should not use inline HTML event attributes to wire up event handlers. That technique is 25+ years old and will not die the death it deserves because people just keep copying it from other code they've seen.
See the comments for the simple explanation:
// Add the event handler to the input in JavaScript, not in HTML
document.getElementById("myID").addEventListener("input", removeElement);
function removeElement(){
// Remove the sibling element that follows the input
document.querySelector("#myID").nextElementSibling.remove();
// Now that the element has been removed, this function is no
// longer required, so remove the event handler to prevent attempts
// to remove it again when it's no longer there. "this" refers to
// the object that caused this function to be invoked (the input
// element in this case).
this.removeEventListener("input", removeElement);
}
<div class="input">
<input type="number" id="myID">
<div>
<h3>MY TEXT</h3>
</div>
</div>

How to remove an HTML element using JavaScript ?
Given an HTML element and the task is to remove the HTML element from the document using JavaScript.
Approach:
Select the HTML element which need to remove.
Use JavaScript remove() and removeChild() method to remove the
element from the HTML document.
Exemple to remove a div :
div.parentNode.removeChild(div);
Follow this link for more information.
I hope I was able to help you.

<div class="input">
<input type="number" id="myID" >
<div id="id2">
<h3>MY TEXT</h3>
</div>
</div>
<script>
document.getElementById("myID").oninput = function() {myFunction()};
function myFunction() {
document.getElementById("id2").innerHTML="";
}
</script>

Problem with using innerHTML is you are basically using a whiteboard. You erase everything on it and you have to redraw it all. That means you would need to reset the value and focus. It is doable, just not practical.
The better thing to do would be to select the element and remove it with .remove()
var field = document.getElementById("myID");
var num = field.value;
if (num.length) {
field.nextElementSibling.remove()
}
It will work, but you will be better off using a class to hide the element. It also has the benefit that if the user deletes the text in the input, you can reshow the message. I would just hide it with a css class with toggle. I would select the div with nextElementSibling.
function myFunction(){
var field = document.getElementById("myID");
var num = field.value;
field.nextElementSibling.classList.toggle('hidden', num.length)
}
.hidden {
display: none;
}
<div class="input">
<input type="number" id="myID" oninput="myFunction()">
<div>
<h3>MY TEXT</h3>
</div>
</div>

Text input and output it on page

I was wondering if I can create a text input where users can type some text and then immediately display them on page, same as twitter. I know about alert window or prompt window but I need something different, a text input on website.
Hope it can be done in JavaScript.

Use .keyup() for the input field then replace the content of the output div.
$(".div-input").keyup(function() {
$(".output").html($(this).val());
});
.output {
margin-top: 20px;
font-size: 2em;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input class="div-input" />
<div class="output">
</div>
If you want to display the input on submit, you could attach a .submit() event on a form tag then use appendTo on the div if you want to insert multiple elements;
$(".form-input").submit(function(e) {
e.preventDefault();
var value = $(".div-input").val();
$("<div class='outputs'>" + value + "</div>").appendTo($(".output"));
});
.output {
margin-top: 20px;
}
.outputs {
padding: 20px;
font-size: 2em;
border: 1px solid black;
margin-bottom: 10px;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<form class="form-input">
<input class="div-input">
<button type="submit">Submit</button>
</form>
<div class="output"></div>

you can use this to show your text anywhere on page
<input id="input-name" oninput="outputname.value = this.value">
<output id="outputname" name="outputname" for="input-name"></output>
You can test it here

If you add an eventlistener to the input, you can use that to change the text in your output area on the page. Like this:
const input = document.getElementById('input');
const output = document.getElementById('output');
input.addEventListener('input', (e) => {
output.innerHTML = input.value;
});
<div id="output"></div>
<input type="text" id="input">

HTML:
<p>Input:</p><input id="input" type="text">
<p>Output:<span id="output"></span></p>
Javascript:
// Function To Select Element
function $(element) {
return document.querySelector(element);
}
// We will get the input when calling this function
function getInput() {
return $('#input').value;
}
// The output will be displayed
function output() {
$('#output').innerHTML = getInput();
}
// This function will start our code
function init() {
output();
}
// On keyup our code will initiate
$('#input').addEventListener('keyup', init);
You can test it here: https://codepen.io/anon/pen/ReyGaO?editors=1111

People are downvoting you because this can be done with very basic JavaScript, and questions like this are very unusual because anyone doing a basic JavaScipt course will probably be able to do this.
Theoretically speaking: you can put an input element and a button on the html page, plus an empty div. You can set an event for the button or even for the input for live updating while typing, and write an event handler function to change the content of the empty div. You can either set its content or add a new child to it, so that the previous content still remains.
Practical example: (The code below is live at https://codepen.io/bradib0y/pen/YJLGrb )
<!DOCTYPE html>
<html>
<body>
<p>Click the button to add a new post.</p>
<input id="NewPostField" type="text" value="Some text">
<button onclick="myFunction()">Add new post</button>
<div id="Posts"></div>
<script>
function myFunction() {
var NewPostField = document.getElementById("NewPostField");
var newPost = document.createElement("p");
newPost.innerHTML = NewPostField.value;
var Posts = document.getElementById("Posts");
Posts.appendChild(newPost);
}
</script>
</body>
</html>

you can do it by this
<input id="mainInput" oninput="output.value = this.value">
<output id="output" name="output" for="input-name"></output>
click here to view in jsFiddle

HTML - Button is cancelled only after second click

I have a very simple code: I want to cancel a button after it's clicked to display something else. I tried this way
HTML:
<div id="container">
<input type="button" value="New game" onclick="newGame()" />
</div>
js:
function newGame() {
var container = document.getElementById("container");
container.removeChild(container.childNodes[0]);
}
What happens is the button gets cancelled only if I click it two times. Where did I get wrong?
I'm sorry if this is a repost, I tried to check but didn't find a quetion identical to mine

It appears as if your code is going to remove the button once you click on it. Is this correct, or are we not looking at the full markup?

If you remove \n (i.e new line) your code will work
try like this
function newGame() {
var container = document.getElementById("container");
debugger;
container.removeChild(container.childNodes[0]);
}
<div id="container"><input type="button" value="New game" onclick="newGame()" /></div>
The reason why your code is not working is, when you hit enter after div, HTML DOM will automatically creates one dummy text node as it's child. hence your input node became the second child for your container.
Working fiddle
Hope it helps :)

try this:
function newGame() {
var container = document.getElementById("container");
// change 0 to 1
container.removeChild(container.childNodes[1]);
}
container.childNodes[0] is a text Node, in which the text is Newline

I gave id to the button and removed it using id.
In your case it is not removing in first time because container.childNodes[0] in first time is not a button. Try your self using console.log in your function.
function newGame() {
var container = document.getElementById("container");
var d_nested = document.getElementById("button_1");
var throwawayNode = container.removeChild(d_nested);
//container.innerHTML='';
}
<div id="container">
<input id="button_1" type="button" value="New game" onclick="newGame()" />
</div>

Alternatively, you could do this:
<div id="container">
<input type="button" value="New game" onclick="document.getElementById('container').removeChild(this);" />
No separate JS file needed.

Toggle issue using input value as id

I'm trying to use jQuery's .toggle() to show and hide one of three divs. The divs have unique ids and the decision which div is got toggled is based on which of the three radio buttons has been selected. The three radio buttons have values that correspond to the ids of the divs. So if someone clicks the -1 radio, the div with the id cMB_0292_A07.m1 should be toggled.
However I'm not getting any response at all and there's no report of any errors in debugger that I've tried. What is wrong?
<!DOCTYPE html>
<html>
<head>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<script>
function showdiv(obj) {
var n = obj.name;
var v = $("input:radio[name='" + n + "']:checked").val();
alert(v);
$("#" + v).toggle();
}
</script>
</head>
<body>
<input name="cMB_0292_A07" value="cMB_0292_A07.m1" onclick="showdiv(this);" type="radio">-1
<input name="cMB_0292_A07" value="cMB_0292_A07.0" onclick="showdiv(this);" type="radio">0
<input name="cMB_0292_A07" value="cMB_0292_A07.p1" onclick="showdiv(this);" type="radio">+1
<div id="cMB_0292_A07.m1" style="display: none">minus1</div>
<div id="cMB_0292_A07.0" style="display: none">zero</div>
<div id="cMB_0292_A07.p1" style="display: none">plus1</div>
</body>
</html>

This is actually a two part issue
First off, you shouldn't have . within IDs.
Secondly, jQuery is seeing this: $('#ID.CLASS')
It is searching the DOM looking for ID: cMB_0292_A07then a child class of m1 for example.
You can fix this, by either removing the periods within your IDs, or using the regex selector [id=""].
$('[id="' + v + '"]').toggle();
jsFiddle DEMO
Other sidenotes, don't use onClick events. It's better to separate your business logic & presentation logic. Use jQuery .on('click', function () {}); events!

You cannot use ., since it will look for its child with class m1 or 0 or p1.
Check out below code snippet:
$(document).ready(function(){
$("input[type='radio']").click(function(){
alert($("#"+$(this).val()).length);
});
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input name="cMB_0292_A07" value="cMB_0292_A07" type="radio">-1
<input name="cMB_0292_A07" value="cMB_0292_A07" type="radio">0
<input name="cMB_0292_A07" value="cMB_0292_A07" type="radio">+1
<div id="cMB_0292_A07" style="display: none">minus1</div>
<div id="cMB_0292_A07" style="display: none">zero</div>
<div id="cMB_0292_A07" style="display: none">plus1</div>

Changing a paragraph via a text field using javascript

I want to type in text in a text field, press a button, and the text of a paragraph will change. What would I need to do for this to happen and is there an easier way to do it other than javascript?
Since I didn't know what I needed to do, here's the code I originally had:
<html>
<head>
<title>Moving Text</title>
<link rel="stylesheet" type="text/css" href="stlye.css">
</head>
<body>
<div id="text">
<p id="new">new text</p>
Main News:<input type="text" name="update"><br>
<input type="button" value="Update" onClick="update();">
<script type="text/javascript">
function update(){
document.getElementById('new').innerHTML = 'Update';
}
</script>
</div>
</body>
I'm pretty sure it's wrong or way off. Any suggestions?

HTML:
<p id="your_paragraph">This text will change, after clicking the button.</p>
Main News: <input type="text" id="theText" />
<input type="button" id="btn" value="Update" />
JavaScript:
var p = document.getElementById('your_paragraph');
var btn = document.getElementById('btn');
var txt = document.getElementById('theText');
btn.onclick = function(){
p.textContent = txt.value;
};
http://jsfiddle.net/3uBKC/

No, you'll need to use javascript. Without an example of your markup nobody will be able to provide you a specific example, but here's a general one using the jQuery library.
// get the textarea, watch for change, paste, and keyup events
$('textarea').on('change paste keyup', function(){
// Store the text field as a variable, get it's value
var thiis = $(this),
value = thiis.val();
// replace the paragraph's content with the textrea's value
$('p').html(value);
});