Develop Reference

Dynamically change the height of the textarea element [duplicate]

There was another thread about this, which I've tried. But there is one problem: the textarea doesn't shrink if you delete the content. I can't find any way to shrink it to the correct size - the clientHeight value comes back as the full size of the textarea, not its contents.
The code from that page is below:
function FitToContent(id, maxHeight)
{
var text = id && id.style ? id : document.getElementById(id);
if ( !text )
return;
var adjustedHeight = text.clientHeight;
if ( !maxHeight || maxHeight > adjustedHeight )
{
adjustedHeight = Math.max(text.scrollHeight, adjustedHeight);
if ( maxHeight )
adjustedHeight = Math.min(maxHeight, adjustedHeight);
if ( adjustedHeight > text.clientHeight )
text.style.height = adjustedHeight + "px";
}
}
window.onload = function() {
document.getElementById("ta").onkeyup = function() {
FitToContent( this, 500 )
};
}

A COMPLETE YET SIMPLE SOLUTION
Updated 2022-08-30
(Added support for single row multiple textbox by default)
The following code will work:
On key input.
With pasted text (right click & ctrl+v).
With cut text (right click & ctrl+x).
With pre-loaded text.
With all textarea's (multiline textbox's) site wide.
With Firefox (v31-109 tested).
With Chrome (v37-108 tested).
With IE (v9-v11 tested).
With Edge (v14-v108 tested).
With IOS Safari.
With Android Browser.
With JavaScript strict mode.
OPTION 1 (With jQuery)
This option requires jQuery and has been tested and is working with 1.7.2 - 3.6.3
Simple (Add this jQuery code to your master script file and forget about it.)
$("textarea").each(function () {
this.setAttribute("style", "height:" + (this.scrollHeight) + "px;overflow-y:hidden;");
}).on("input", function () {
this.style.height = 0;
this.style.height = (this.scrollHeight) + "px";
});
<script src="https://ajax.aspnetcdn.com/ajax/jQuery/jquery-3.6.3.min.js"></script>
<textarea placeholder="Type, paste, cut text here...">PRELOADED TEXT.
This JavaScript should now add better support for IOS browsers and Android browsers.</textarea>
<textarea placeholder="Type, paste, cut text here..."></textarea>
Test on jsfiddle
OPTION 2 (Pure JavaScript)
Simple (Add this JavaScript to your master script file and forget about it.)
const tx = document.getElementsByTagName("textarea");
for (let i = 0; i < tx.length; i++) {
tx[i].setAttribute("style", "height:" + (tx[i].scrollHeight) + "px;overflow-y:hidden;");
tx[i].addEventListener("input", OnInput, false);
}
function OnInput() {
this.style.height = 0;
this.style.height = (this.scrollHeight) + "px";
}
<textarea placeholder="Type, paste, cut text here...">PRELOADED TEXT. This JavaScript should now add better support for IOS browsers and Android browsers.</textarea>
<textarea placeholder="Type, paste, cut text here..."></textarea>
Test on jsfiddle
OPTION 3 (jQuery Extension)
Useful if you want to apply further chaining to the textareas, you want to be auto-sized.
jQuery.fn.extend({
autoHeight: function () {
function autoHeight_(element) {
return jQuery(element)
.css({ "height": 0, "overflow-y": "hidden" })
.height(element.scrollHeight);
}
return this.each(function() {
autoHeight_(this).on("input", function() {
autoHeight_(this);
});
});
}
});
Invoke with $("textarea").autoHeight()
UPDATING TEXTAREA VIA JAVASCRIPT
When injecting content into a textarea via JavaScript, append the following code to invoke the function in option 1.
$("textarea").trigger("input");
PRESET TEXTAREA HEIGHT
To fix the initial height of the textarea you will need to add another condition:
const txHeight = 16;
const tx = document.getElementsByTagName("textarea");
for (let i = 0; i < tx.length; i++) {
if (tx[i].value == '') {
tx[i].setAttribute("style", "height:" + txHeight + "px;overflow-y:hidden;");
} else {
tx[i].setAttribute("style", "height:" + (tx[i].scrollHeight) + "px;overflow-y:hidden;");
}
tx[i].addEventListener("input", OnInput, false);
}
function OnInput(e) {
this.style.height = 0;
this.style.height = (this.scrollHeight) + "px";
}
<textarea placeholder="Type, paste, cut text here...">PRELOADED TEXT. This JavaScript should now add better support for IOS browsers and Android browsers.</textarea>
<textarea placeholder="Type, paste, cut text here..."></textarea>

This works for me (Firefox 3.6/4.0 and Chrome 10/11):
var observe;
if (window.attachEvent) {
observe = function (element, event, handler) {
element.attachEvent('on'+event, handler);
};
}
else {
observe = function (element, event, handler) {
element.addEventListener(event, handler, false);
};
}
function init () {
var text = document.getElementById('text');
function resize () {
text.style.height = 'auto';
text.style.height = text.scrollHeight+'px';
}
/* 0-timeout to get the already changed text */
function delayedResize () {
window.setTimeout(resize, 0);
}
observe(text, 'change', resize);
observe(text, 'cut', delayedResize);
observe(text, 'paste', delayedResize);
observe(text, 'drop', delayedResize);
observe(text, 'keydown', delayedResize);
text.focus();
text.select();
resize();
}
textarea {
border: 0 none white;
overflow: hidden;
padding: 0;
outline: none;
background-color: #D0D0D0;
}
<body onload="init();">
<textarea rows="1" style="height:1em;" id="text"></textarea>
</body>
If you want try it on jsfiddle
It starts with a single line and grows only the exact amount necessary. It is ok for a single textarea, but I wanted to write something where I would have many many many such textareas (about as much as one would normally have lines in a large text document). In that case it is really slow. (In Firefox it's insanely slow.) So I really would like an approach that uses pure CSS. This would be possible with contenteditable, but I want it to be plaintext-only.

jQuery solution
adjust the css to match your requirements
css...
div#container textarea {
min-width: 270px;
width: 270px;
height: 22px;
line-height: 24px;
min-height: 22px;
overflow-y: hidden; /* fixes scrollbar flash - kudos to #brettjonesdev */
padding-top: 1.1em; /* fixes text jump on Enter keypress */
}
javascript...
// auto adjust the height of
$('#container').delegate( 'textarea', 'keydown', function (){
$(this).height( 0 );
$(this).height( this.scrollHeight );
});
$('#container').find( 'textarea' ).keydown();
OR alternative for jQuery 1.7+...
// auto adjust the height of
$('#container').on( 'keyup', 'textarea', function (){
$(this).height( 0 );
$(this).height( this.scrollHeight );
});
$('#container').find( 'textarea' ).keyup();
I've created a fiddle with the absolute minimum styling as a starting point for your experiments...
http://jsfiddle.net/53eAy/951/

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Textarea autoresize</title>
<style>
textarea {
overflow: hidden;
}
</style>
<script>
function resizeTextarea(ev) {
this.style.height = '24px';
this.style.height = this.scrollHeight + 12 + 'px';
}
var te = document.querySelector('textarea');
te.addEventListener('input', resizeTextarea);
</script>
</head>
<body>
<textarea></textarea>
</body>
</html>
Tested in Firefox 14 and Chromium 18. The numbers 24 and 12 are arbitrary, test to see what suits you best.
You could do without the style and script tags, but it becomes a bit messy imho (this is old style HTML+JS and is not encouraged).
<textarea style="overflow: hidden" onkeyup="this.style.height='24px'; this.style.height = this.scrollHeight + 12 + 'px';"></textarea>
Edit: modernized code. Changed onkeyup attribute to addEventListener.
Edit: keydown works better than keyup
Edit: declare function before using
Edit: input works better than keydown (thnx #WASD42 & #MA-Maddin)
jsfiddle

The best solution (works and is short) for me is:
$(document).on('input', 'textarea', function () {
$(this).outerHeight(38).outerHeight(this.scrollHeight); // 38 or '1em' -min-height
});
It works like a charm without any blinking with paste (with mouse also), cut, entering and it shrinks to the right size.
Please take a look at jsFiddle.

Found an one liner from here;
<textarea name="text" oninput="this.style.height = ''; this.style.height = this.scrollHeight +'px'"></textarea>

If you don’t need to support IE8 you can use the input event:
var resizingTextareas = [].slice.call(document.querySelectorAll('textarea[autoresize]'));
resizingTextareas.forEach(function(textarea) {
textarea.addEventListener('input', autoresize, false);
});
function autoresize() {
this.style.height = 'auto';
this.style.height = this.scrollHeight+'px';
this.scrollTop = this.scrollHeight;
window.scrollTo(window.scrollLeft,(this.scrollTop+this.scrollHeight));
}
Now you only need to add some CSS and you are done:
textarea[autoresize] {
display: block;
overflow: hidden;
resize: none;
}
Usage:
<textarea autoresize>Type here and I’ll resize.</textarea>
You can read more about how it works on my blog post.

You're using the higher value of the current clientHeight and the content scrollHeight. When you make the scrollHeight smaller by removing content, the calculated area can't get smaller because the clientHeight, previously set by style.height, is holding it open. You could instead take a max() of scrollHeight and a minimum height value you have predefined or calculated from textarea.rows.
In general you probably shouldn't really rely on scrollHeight on form controls. Apart from scrollHeight being traditionally less widely-supported than some of the other IE extensions, HTML/CSS says nothing about how form controls are implemented internally and you aren't guaranteed scrollHeight will be anything meaningful. (Traditionally some browsers have used OS widgets for the task, making CSS and DOM interaction on their internals impossible.) At least sniff for scrollHeight/clientHeight's existance before trying to enable the effect.
Another possible alternative approach to avoid the issue if it's important that it work more widely might be to use a hidden div sized to the same width as the textarea, and set in the same font. On keyup, you copy the text from the textarea to a text node in hidden div (remembering to replace '\n' with a line break, and escape '<'/'&' properly if you're using innerHTML). Then simply measuring the div's offsetHeight will give you the height you need.

autosize
https://github.com/jackmoore/autosize
Just works, standalone, is popular (3.0k+ GitHub stars as of October 2018), available on cdnjs) and lightweight (~3.5k). Demo:
<textarea id="autosize" style="width:200px;">a
J b
c</textarea>
<script src="https://cdnjs.cloudflare.com/ajax/libs/autosize.js/4.0.2/autosize.min.js"></script>
<script>autosize(document.querySelectorAll('#autosize'));</script>
BTW, if you are using the ACE editor, use maxLines: Infinity: Automatically adjust height to contents in Ace Cloud 9 editor

As a different approach, you can use a <span> which adjusts its size automatically. You will need make it editable by adding the contenteditable="true" property and you're done:
div {
width: 200px;
}
span {
border: 1px solid #000;
padding: 5px;
}
<div>
<span contenteditable="true">This text can be edited by the user</span>
</div>
The only issue with this approach is that if you want to submit the value as part of the form, you'll have to do so by yourself in JavaScript. Doing so is relatively easy. For example, you can add a hidden field and in the onsubmit event of the form assign the value of the span to the hidden field which will be then automatically submitted with the form.

There is a slightly different approach.
<div style="position: relative">
<pre style="white-space: pre-wrap; word-wrap: break-word"></pre>
<textarea style="position: absolute; top: 0; left: 0; width: 100%; height: 100%"></textarea>
</div>
The idea is to copy the text from textarea into the pre and let CSS make sure that they have the same size.
The benefit is that frameworks present simple tools to move text around without touching any events. Namely, in AngularJS you would add a ng-model="foo" ng-trim="false" to the textarea and ng-bind="foo + '\n'" to the pre. See a fiddle.
Just make sure that pre has the same font size as the textarea.

Has anyone considered contenteditable? No messing around with scrolling,a nd the only JS I like about it is if you plan on saving the data on blur... and apparently, it's compatible on all of the popular browsers : http://caniuse.com/#feat=contenteditable
Just style it to look like a text box, and it autosizes... Make its min-height the preferred text height and have at it.
What's cool about this approach is that you can save and tags on some of the browsers.
http://jsfiddle.net/gbutiri/v31o8xfo/
var _auto_value = '';
$(document).on('blur', '.autosave', function(e) {
var $this = $(this);
if ($this.text().trim() == '') {
$this.html('');
}
// The text is here. Do whatever you want with it.
$this.addClass('saving');
if (_auto_value !== $this.html() || $this.hasClass('error')) {
// below code is for example only.
$.ajax({
url: '/echo/json/?action=xyz_abc',
data: 'data=' + $this.html(),
type: 'post',
datatype: 'json',
success: function(d) {
console.log(d);
$this.removeClass('saving error').addClass('saved');
var k = setTimeout(function() {
$this.removeClass('saved error')
}, 500);
},
error: function() {
$this.removeClass('saving').addClass('error');
}
});
} else {
$this.removeClass('saving');
}
}).on('focus mouseup', '.autosave', function() {
var $this = $(this);
if ($this.text().trim() == '') {
$this.html('');
}
_auto_value = $this.html();
}).on('keyup', '.autosave', function(e) {
var $this = $(this);
if ($this.text().trim() == '') {
$this.html('');
}
});
body {
background: #3A3E3F;
font-family: Arial;
}
label {
font-size: 11px;
color: #ddd;
}
.autoheight {
min-height: 16px;
font-size: 16px;
margin: 0;
padding: 10px;
font-family: Arial;
line-height: 20px;
box-sizing: border-box;
-o-box-sizing: border-box;
-moz-box-sizing: border-box;
-webkit-box-sizing: border-box;
overflow: hidden;
display: block;
resize: none;
border: 0;
outline: none;
min-width: 200px;
background: #ddd;
max-height: 400px;
overflow: auto;
}
.autoheight:hover {
background: #eee;
}
.autoheight:focus {
background: #fff;
}
.autosave {
-webkit-transition: all .2s;
-moz-transition: all .2s;
transition: all .2s;
position: relative;
float: none;
}
.autoheight * {
margin: 0;
padding: 0;
}
.autosave.saving {
background: #ff9;
}
.autosave.saved {
background: #9f9;
}
.autosave.error {
background: #f99;
}
.autosave:hover {
background: #eee;
}
.autosave:focus {
background: #fff;
}
[contenteditable=true]:empty:before {
content: attr(placeholder);
color: #999;
position: relative;
top: 0px;
/*
For IE only, do this:
position: absolute;
top: 10px;
*/
cursor: text;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<label>Your Name</label>
<div class="autoheight autosave contenteditable" contenteditable="true" placeholder="Your Name"></div>

The following works for cutting, pasting, etc., regardless of whether those actions are from the mouse, a keyboard shortcut, selecting an option from a menu bar ... several answers take a similar approach but they don't account for box-sizing, which is why they incorrectly apply the style overflow: hidden.
I do the following, which also works well with max-height and rows for minimum and maximum height.
function adjust() {
var style = this.currentStyle || window.getComputedStyle(this);
var boxSizing = style.boxSizing === 'border-box'
? parseInt(style.borderBottomWidth, 10) +
parseInt(style.borderTopWidth, 10)
: 0;
this.style.height = '';
this.style.height = (this.scrollHeight + boxSizing) + 'px';
};
var textarea = document.getElementById("ta");
if ('onpropertychange' in textarea) { // IE
textarea.onpropertychange = adjust;
} else if ('oninput' in textarea) {
textarea.oninput = adjust;
}
setTimeout(adjust.bind(textarea));
textarea {
resize: none;
max-height: 150px;
border: 1px solid #999;
outline: none;
font: 18px sans-serif;
color: #333;
width: 100%;
padding: 8px 14px;
box-sizing: border-box;
}
<textarea rows="3" id="ta">
Try adding several lines to this.
</textarea>
For absolute completeness, you should call the adjust function in a few more circumstances:
Window resize events, if the width of the textarea changes with window resizing, or other events that change the width of the textarea
When the textarea's display style attribute changes, e.g. when it goes from none (hidden) to block
When the value of the textarea is changed programmatically
Note that using window.getComputedStyle or getting currentStyle can be somewhat computationally expensive, so you may want to cache the result instead.
Works for IE6, so I really hope that's good enough support.

I used the following code for multiple textareas. Working fine in Chrome 12, Firefox 5 and IE 9, even with delete, cut and paste actions performed in the textareas.
function attachAutoResizeEvents() {
for (i = 1; i <= 4; i++) {
var txtX = document.getElementById('txt' + i)
var minH = txtX.style.height.substr(0, txtX.style.height.indexOf('px'))
txtX.onchange = new Function("resize(this," + minH + ")")
txtX.onkeyup = new Function("resize(this," + minH + ")")
txtX.onchange(txtX, minH)
}
}
function resize(txtX, minH) {
txtX.style.height = 'auto' // required when delete, cut or paste is performed
txtX.style.height = txtX.scrollHeight + 'px'
if (txtX.scrollHeight <= minH)
txtX.style.height = minH + 'px'
}
window.onload = attachAutoResizeEvents
textarea {
border: 0 none;
overflow: hidden;
outline: none;
background-color: #eee
}
<textarea style='height:100px;font-family:arial' id="txt1"></textarea>
<textarea style='height:125px;font-family:arial' id="txt2"></textarea>
<textarea style='height:150px;font-family:arial' id="txt3"></textarea>
<textarea style='height:175px;font-family:arial' id="txt4"></textarea>

A bit corrections. Works perfectly in Opera
$('textarea').bind('keyup keypress', function() {
$(this).height('');
var brCount = this.value.split('\n').length;
this.rows = brCount+1; //++ To remove twitching
var areaH = this.scrollHeight,
lineHeight = $(this).css('line-height').replace('px',''),
calcRows = Math.floor(areaH/lineHeight);
this.rows = calcRows;
});

I Don't know if anyone mention this way but in some cases it's possible to resize the height with rows Attribute
textarea.setAttribute('rows',breaks);
Demo

Here is an angularjs directive for panzi's answer.
module.directive('autoHeight', function() {
return {
restrict: 'A',
link: function(scope, element, attrs) {
element = element[0];
var resize = function(){
element.style.height = 'auto';
element.style.height = (element.scrollHeight)+'px';
};
element.addEventListener('change', resize, false);
element.addEventListener('cut', resize, false);
element.addEventListener('paste', resize, false);
element.addEventListener('drop', resize, false);
element.addEventListener('keydown',resize, false);
setTimeout(resize, 100);
}
};
});
HTML:
<textarea ng-model="foo" auto-height></textarea>

I know a short and correct way of implementing this with jquery.No extra hidden div needed and works in most browser
<script type="text/javascript">$(function(){
$("textarea").live("keyup keydown",function(){
var h=$(this);
h.height(60).height(h[0].scrollHeight);//where 60 is minimum height of textarea
});});
</script>

Some of the answers here don't account for padding.
Assuming you have a maxHeight you don't want to go over, this worked for me:
// obviously requires jQuery
// element is the textarea DOM node
var $el = $(element);
// inner height is height + padding
// outerHeight includes border (and possibly margins too?)
var padding = $el.innerHeight() - $el.height();
var originalHeight = $el.height();
// XXX: Don't leave this hardcoded
var maxHeight = 300;
var adjust = function() {
// reset it to the original height so that scrollHeight makes sense
$el.height(originalHeight);
// this is the desired height (adjusted to content size)
var height = element.scrollHeight - padding;
// If you don't want a maxHeight, you can ignore this
height = Math.min(height, maxHeight);
// Set the height to the new adjusted height
$el.height(height);
}
// The input event only works on modern browsers
element.addEventListener('input', adjust);

An even simpler, cleaner approach is this:
// adjust height of textarea.auto-height
$(document).on( 'keyup', 'textarea.auto-height', function (e){
$(this).css('height', 'auto' ); // you can have this here or declared in CSS instead
$(this).height( this.scrollHeight );
}).keyup();
// and the CSS
textarea.auto-height {
resize: vertical;
max-height: 600px; /* set as you need it */
height: auto; /* can be set here of in JS */
overflow-y: auto;
word-wrap:break-word
}
All that is needed is to add the .auto-height class to any textarea you want to target.
Tested in FF, Chrome and Safari. Let me know if this doesn't work for you, for any reason. But, this is the cleanest and simplest way I've found this to work. And it works great! :D

You can use JQuery to expand the textarea while typing:
$(document).find('textarea').each(function () {
var offset = this.offsetHeight - this.clientHeight;
$(this).on('keyup input focus', function () {
$(this).css('height', 'auto').css('height', this.scrollHeight + offset);
});
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div>
<textarea name="note"></textarea>
<div>

Those who want to achieve the same in new versions of Angular.
Grab textArea elementRef.
#ViewChild('textArea', { read: ElementRef }) textArea: ElementRef;
public autoShrinkGrow() {
textArea.style.overflow = 'hidden';
textArea.style.height = '0px';
textArea.style.height = textArea.scrollHeight + 'px';
}
<textarea (keyup)="autoGrow()" #textArea></textarea>
I am also adding another use case that may come handy some users reading the thread, when user want to increase the height of text-area to certain height and then have overflow:scroll on it, above method can be extended to achieve the mentioned use-case.
public autoGrowShrinkToCertainHeight() {
const textArea = this.textArea.nativeElement;
if (textArea.scrollHeight > 77) {
textArea.style.overflow = 'auto';
return;
}
else {
textArea.style.overflow = 'hidden';
textArea.style.height = '0px';
textArea.style.height = textArea.scrollHeight + 'px';
}
}

my implementation is very simple, count the number of lines in the input (and minimum 2 rows to show that it's a textarea):
textarea.rows = Math.max(2, textarea.value.split("\n").length) // # oninput
full working example with stimulus: https://jsbin.com/kajosolini/1/edit?html,js,output
(and this works with the browser's manual resize handle for instance)

This code works for pasting and select delete also.
onKeyPressTextMessage = function(){
var textArea = event.currentTarget;
textArea.style.height = 'auto';
textArea.style.height = textArea.scrollHeight + 'px';
};
<textarea onkeyup="onKeyPressTextMessage(event)" name="welcomeContentTmpl" id="welcomeContent" onblur="onblurWelcomeTitle(event)" rows="2" cols="40" maxlength="320"></textarea>
Here is the JSFiddle

I recommend the javascript library from http://javierjulio.github.io/textarea-autosize.
Per comments, add example codeblock on plugin usage:
<textarea class="js-auto-size" rows="1"></textarea>
<script src="http://code.jquery.com/jquery-2.1.0.min.js"></script>
<script src="jquery.textarea_autosize.min.js"></script>
<script>
$('textarea.js-auto-size').textareaAutoSize();
</script>
Minimum required CSS:
textarea {
box-sizing: border-box;
max-height: 160px; // optional but recommended
min-height: 38px;
overflow-x: hidden; // for Firefox (issue #5)
}

MakeTextAreaResisable that uses qQuery
function MakeTextAreaResisable(id) {
var o = $(id);
o.css("overflow-y", "hidden");
function ResizeTextArea() {
o.height('auto');
o.height(o[0].scrollHeight);
}
o.on('change', function (e) {
ResizeTextArea();
});
o.on('cut paste drop keydown', function (e) {
window.setTimeout(ResizeTextArea, 0);
});
o.focus();
o.select();
ResizeTextArea();
}

None of the answers seem to work. But this one works for me:
https://coderwall.com/p/imkqoq/resize-textarea-to-fit-content
$('#content').on( 'change keyup keydown paste cut', 'textarea', function (){
$(this).height(0).height(this.scrollHeight);
}).find( 'textarea' ).change();

Accepted answer is working fine. But that is lot of code for this simple functionality. The below code will do the trick.
$(document).on("keypress", "textarea", function (e) {
var height = $(this).css("height");
var iScrollHeight = $(this).prop("scrollHeight");
$(this).css('height',iScrollHeight);
});

An example implementation with React:
const {
useLayoutEffect,
useState,
useRef
} = React;
const TextArea = () => {
const ref = useRef();
const [value, setValue] = useState('Some initial text that both wraps and uses\nnew\nlines');
// This only tracks the auto-sized height so we can tell if the user has manually resized
const autoHeight = useRef();
useLayoutEffect(() => {
if (!ref.current) {
return;
}
if (
autoHeight.current !== undefined &&
ref.current.style.height !== autoHeight.current
) {
// don't auto size if the user has manually changed the height
return;
}
ref.current.style.height = "auto";
ref.current.style.overflow = "hidden";
const next = `${ref.current.scrollHeight}px`;
ref.current.style.height = next;
autoHeight.current = next;
ref.current.style.overflow = "auto";
}, [value, ref, autoHeight]);
return (
<textarea
ref={ref}
style={{
resize: 'vertical',
minHeight: '1em',
}}
value={value}
onChange={event => setValue(event.target.value)}
/>
);
}
ReactDOM.render(<TextArea />, document.getElementById('app'))
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/17.0.1/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/17.0.1/umd/react-dom.production.min.js"></script>
<div id="app"></div>

A simple way to do using React.
...
const textareaRef = useRef();
const handleChange = (e) => {
textareaRef.current.style.height = "auto";
textareaRef.current.style.height = textareaRef.current.scrollHeight + "px";
};
return <textarea ref={textareaRef} onChange={handleChange} />;

Change Element style with window height with JavaScript

I'm trying to change the background colour of a div element when the page window height is lower than a certain value using JavaScript. I have a vague idea of how this might work but it doesn't seem to be having any effect.
This is within a tag and loads after the body of my HTML.
<script>
var footer = document.getElementByClassName("footer");
if (window.innerHeight < 800) {
footer.style.backgroundColor = 'black';
}
</script>

Like already mentioned getElementsByClassName returns an array. You had a typo there so nothing was returned, however.
As long as there's only 1 element with the class name "footer" this should work (might be better to use an ID):
<script>
var footer = document.getElementsByClassName("footer")[0];
if (window.innerHeight < 800) {
footer.style.backgroundColor = 'black';
}
</script>
But yeah, you should really look at the dev console when you're writing Javascript. It can save a lot of headaches!

JavaScript does not have a method called getElementByClassName.
The closest thing is getElementsByClassName which returns an HTMLCollection which is an array-like object, so to get the first element in the list you have use an index:
var footer = document.getElementsByClassName('footer')[0];
You can also use querySelector to get the first element with the class name:
var footer = document.querySelector('.footer');
Here is a working example:
var footer = document.getElementsByClassName('footer')[0];
window.onresize = function (event) {
if (window.innerHeight < 800) {
footer.style.backgroundColor = 'black';
} else {
footer.style.backgroundColor = 'blue';
}
}
.footer {
height: 50px;
width: 100%;
background: black;
}
<footer class="footer"></footer>
JSFiddle Demo http://jsfiddle.net/moogs/x63rc6v4/1/

Change DIV margin on interval

I am trying to change the margin of each element, using setAttribute.
How can I able to use my variable dist "distance" to decrease value until 10, every after delay "interval"?
var dist=200; var speed = 2000;
function slideLeft(x){
dist--;
slideSet[x].setAttribute("style","margin-right:"+dist+"px;");
setTimeout(slideLeft(x), delay);
}
Take these style and elements for example...
.widiv { margin-right:200px; }
<div>
<div class="widiv" ></div>
<div class="widiv" ></div>
</div>
Thanks a lot.

Here's your code with some changes: See fiddle http://jsfiddle.net/chrismoutray/4p3xX/
var dist = 200, delay = 500,
slideSet = document.getElementsByTagName('div');
function slideLeft(x) {
dist--;
if (dist < 0) return;
slideSet[x].setAttribute("style", "margin-right:" + dist + "px;");
setTimeout(function() {
slideLeft(x);
}, delay);
}
slideLeft(1);
With a few additions to the styling:
.widiv {
margin-right:200px;
float:left;
width: 100px;
border: 1px solid black;
height: 100px; }
The main differences are that when calling setTimeout I'm using a function delegate (function() { <your code here> }) to call the slideLeft method so that x variable is used correctly - I don't think you can pass a statement into setTimeout without doing it this way.
Also in styling the divs I made sure to include a float left other wise the change to margin right doesn't make sense - should this be margin left instead?

Resize on div element

jQuery has the resize() - event, but it just work with window.
jQuery(window).resize(function() { /* What ever */ });
This works fine! But when I want to add the event to a div element it doesn't work.
E.g.
jQuery('div').resize(function() { /* What ever */ });
I want to start an callback when the size of a div-element has changed. I don't want to start a resizable - event – just a event to check if the size of a div -
element has changed.
Is there any solution to do this?

DIV does not fire a resize event, so you won't be able to do exactly what you've coded, but you could look into monitoring DOM properties.
If you are actually working with something like resizables, and that is the only way for a div to change in size, then your resize plugin will probably be implementing a callback of its own.

I was only interested for a trigger when a width of an element was changed (I don' care about height), so I created a jquery event that does exactly that, using an invisible iframe element.
$.event.special.widthChanged = {
remove: function() {
$(this).children('iframe.width-changed').remove();
},
add: function () {
var elm = $(this);
var iframe = elm.children('iframe.width-changed');
if (!iframe.length) {
iframe = $('<iframe/>').addClass('width-changed').prependTo(this);
}
var oldWidth = elm.width();
function elmResized() {
var width = elm.width();
if (oldWidth != width) {
elm.trigger('widthChanged', [width, oldWidth]);
oldWidth = width;
}
}
var timer = 0;
var ielm = iframe[0];
(ielm.contentWindow || ielm).onresize = function() {
clearTimeout(timer);
timer = setTimeout(elmResized, 20);
};
}
}
It requires the following css :
iframe.width-changed {
width: 100%;
display: block;
border: 0;
height: 0;
margin: 0;
}
You can see it in action here widthChanged fiddle

// this is a Jquery plugin function that fires an event when the size of an element is changed
// usage: $().sizeChanged(function(){})
(function ($) {
$.fn.sizeChanged = function (handleFunction) {
var element = this;
var lastWidth = element.width();
var lastHeight = element.height();
setInterval(function () {
if (lastWidth === element.width()&&lastHeight === element.height())
return;
if (typeof (handleFunction) == 'function') {
handleFunction({ width: lastWidth, height: lastHeight },
{ width: element.width(), height: element.height() });
lastWidth = element.width();
lastHeight = element.height();
}
}, 100);
return element;
};
}(jQuery));

I've created jquery plugin jquery.resize it use resizeObserver if supported or solution based on marcj/css-element-queries scroll event, no setTimeout/setInterval.
You use just
jQuery('div').on('resize', function() { /* What ever */ });
or as resizer plugin
jQuery('div').resizer(function() { /* What ever */ });
I've created this for jQuery Terminal and extracted into separated repo and npm package, but in a mean time I switched to hidden iframe because I had problems with resize if element was inside iframe. I may update the plugin accordingly. You can look at iframe based resizer plugin in jQuery Terminal source code.
EDIT: new version use iframe and resize on it's window object because the previous solutions was not working when page was inside iframe.
EDIT2: Because the fallback use iframe you can't use it with form controls or images, you need to add it to the wrapper element.
EDIT3:: there is better solution using resizeObserver polyfill that use mutation observer (if resizeObserver is not supported) and work even in IE. It also have TypeScript typings.

what about this:
divH = divW = 0;
jQuery(document).ready(function(){
divW = jQuery("div").width();
divH = jQuery("div").height();
});
function checkResize(){
var w = jQuery("div").width();
var h = jQuery("div").height();
if (w != divW || h != divH) {
/*what ever*/
divH = h;
divW = w;
}
}
jQuery(window).resize(checkResize);
var timer = setInterval(checkResize, 1000);
BTW I suggest you to add an id to the div and change the $("div") to $("#yourid"), it's gonna be faster, and it won't break when later you add other divs

There is a really nice, easy to use, lightweight (uses native browser events for detection) plugin for both basic JavaScript and for jQuery that was released this year. It performs perfectly:
https://github.com/sdecima/javascript-detect-element-resize

Only window is supported yes but you could use a plugin for it: http://benalman.com/projects/jquery-resize-plugin/

There now exists Resize Observer
You could use it like so:
const resizeObserver = new ResizeObserver((entries) => {
entries.forEach(console.log);
})
resizeObserver.observe(document.getElementById("ExampleElement"));

For a google maps integration I was looking for a way to detect when a div has changed in size. Since google maps always require proper dimensions e.g. width and height in order to render properly.
The solution I came up with is a delegation of an event, in my case a tab click. This could be a window resize of course, the idea remains the same:
if (parent.is(':visible')) {
w = parent.outerWidth(false);
h = w * mapRatio /*9/16*/;
this.map.css({ width: w, height: h });
} else {
this.map.closest('.tab').one('click', function() {
this.activate();
}.bind(this));
}
this.map in this case is my map div.
Since my parent is invisible on load, the computed width and height are 0 or don't match.
By using .bind(this) I can delegate the script execution (this.activate) to an event (click).
Now I'm confident the same applies for resize events.
$(window).one('resize', function() {
this.div.css({ /*whatever*/ });
}.bind(this));
Hope it helps anyone!

You can change your text or Content or Attribute depend on Screen size:
HTML:
<p class="change">Frequently Asked Questions (FAQ)</p>
<p class="change">Frequently Asked Questions </p>
Javascript:
<script>
const changeText = document.querySelector('.change');
function resize() {
if((window.innerWidth<500)&&(changeText.textContent="Frequently Asked Questions (FAQ)")){
changeText.textContent="FAQ";
} else {
changeText.textContent="Frequently Asked Questions (FAQ)";
}
}
window.onresize = resize;
</script>

document.addEventListener('transitionend', function(e) {
if ($(e.target).is("div")) {
$("div").text("width: "+$("div").width());
}
});
$("div").css({"width":"150px"});
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div style="width: 100px;transition-delay: 0.000000001s;">width: 100</div>

A very simple implementation.
<script>
var move = function(e) {
if ((e.w && e.w !== e.offsetWidth) || (e.h && e.h !== e.offsetHeight)) {
new Function(e.getAttribute('onresize')).call(e);
}
e.w = e.offsetWidth;
e.h = e.offsetHeight;
}
var resize = function() {
console.log('Resized')
}
</script>
<style>
.resizable {
resize: both;
overflow: auto;
width: 200px;
border: 1px solid black;
padding: 20px;
}
</style>
<div class='resizable' onresize="resize(this)" onmousemove="move(this)">
Pure vanilla implementation
</div>

If you just want to resize the div itself you need to specify that in css style. You need to add overflow and resize property.
Below is my code snippet
#div1 {
width: 90%;
height: 350px;
padding: 10px;
border: 1px solid #aaaaaa;
overflow: auto;
resize: both;
}
<div id="div1">
</div>

JavaScript div creation

Need a small hand here im trying to combine two functions to create a program that takes text from a text area and inserts it into a div (managed that with the first code) the second peace of code im trying to create a div each time, what id like to do is everytime some one writes in the textarea and "posts" the message it will create a new div (rather than the first code which overwrites if anything new is posted).
$(function () {
$('button').click(function () {
var x = $('textarea').val();
$('#test').html(x);
return false;
});
});
second:
function creatediv(id, html, width, height, left, top) {
var newdiv = document.createElement('div');
newdiv.setAttribute('id', id);
if (width) {
newdiv.style.width = 300;
}
if (height) {
newdiv.style.height = 300;
}
if ((left || top) || (left && top)) {
newdiv.style.position = "absolute";
if (left) {
newdiv.style.left = left;
}
if (top) {
newdiv.style.top = top;
}
}
newdiv.style.background = "#00C";
newdiv.style.border = "4px solid #000";
if (html) {
newdiv.innerHTML = html;
} else {
newdiv.innerHTML = "nothing";
}
document.body.appendChild(newdiv);
}
Being careful tho as I have divs set by css for my master page in asp, dont want to overwrite them. Its important I dont add them to the same div aswell as I will be adding more code later that will contain a button inside the created div to add comments to that div only.
Thanks to any and all that can help!

Yeah, don't bother re-inventing the wheel. Get a library like jQuery and learn it. Faster, easier.
http://jquery.com/
But since jquery is one of your tags, I take it that you are using it?
In that case, just use append:
http://api.jquery.com/append/
$(function () {
$('button').click(function () {
var x = $('textarea').val();
$('#test').append(x);
return false;
});
});

Basically it would be:
$(function () {
$('button').click(function () {
var x = $('textarea').val();
creatediv(..., x, ...);
return false;
});
});
However you'd need to provide the other parameters (id, width, height, left, top) of your function somehow. From your description I can't say what you would want to use there.
BTW, your creatediv has errors. The style properties width, height(and leftand top) require units, so you have to use (for example):
newdiv.style.width = "300px";

See the DEMO
I think that's what u wanted to do.