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How do I get a div created in js to fill the screen after clicking on a dynamically created td?

I'm creating a jeopardy style game where if you click on a dynamically created td containing the dollar amount pertaining to a question, the question (already obtained from Jeopardy API) is placed as an innerText inside a dynamically created div element. After clicking on the td, I want the div to animate and fill the entire screen.
This is a little snippet.
handleClick(e) {
let targetID = e.target.id;
if (this.lockboard) return;
for (let x = 0; x < this.width; x++) {
for (let y = 0; y < this.height - 1; y++) {
if (targetID.includes(`${y}-${x}`) && targetID) {
this.lockboard = true;
let newDiv = document.createElement('DIV');
let clickedTD = document.getElementById(`${y}-${x}`);
console.log(clickedTD);
newDiv.innerText = this.clues[x][y].question;
newDiv.classList.add('zoom-in');
console.log(this.clues[x][y].question);
console.log(this.clues[x][y].answer);
}
this.lockboard = false;
}
}
}
handleClick is the callback passed to an event Listener on the dynamically created td in an instance method.
The .zoom-in class in CSS has the following code:
.zoom-in {
color: white;
position: absolute;
transform: scale(1) translate(100%, 100%);
transition: transform 3s;
}
TDLR: I guess I just don't know how to animate the div to blow up and fill the whole screen after clicking the TD

The class zoom-in can expand the element it targets to full screen and height.
.zoom-in {
color: white;
position: absolute;
width: 100vw;
height: 100vh;
transition: width 3s, height 3s;
}

Try to add property background-color. Not sure if this could solve a problem.
.zoom-in {
background-color: #000;
color: white;
position: absolute;
width: 100vw;
height: 100vh;
transition: width 3s, height 3s;
}

Animating a div element

Looking to make a specific animation for a div element. I want it to go down (smoothly) and when it reaches the bottom of the screen to come back up (smoothly).
The code I have is as follows:
The Javascript part at the If statement is where I am having difficulties. I want the box to come down and come back up smoothly.
HTML:
<div class="verticalDiv" id="verticalDiv" onclick="verticalMove()"></div>
CSS:
.verticalDiv {
position: absolute;
top: 0px;
right: 500px;
width: 100px;
height: 100px;
margin: 100px auto;
background: red;
}
JS:
myVar1 = setInterval(verticalMove, 50);
v = 0;
function verticalMove() {
redBox = document.getElementById('verticalDiv')
redBox.style.top = v + "px";
if (v >= 0) {
v++;}
if (v === 200) {
v--;
}
console.log(v);
}

I think, best way is to use css animation. You don't have to care about animation logic. Just use keyframes.
Here is example:
HTML
<div id="verticalDiv" class="verticalDiv"></div>
CSS
.verticalDiv {
height: 20px;
width: 20px;
background: red;
}
#keyframes move {
0% { transform: translateY(0); }
50% { transform: translateY(200px); }
100% { transform: translateY(0); }
}
.verticalDiv.move {
animation: move 3s ease-in-out;
}
JS
const verticalDiv = document.getElementById('verticalDiv');
verticalDiv.addEventListener('click', () => {
verticalDiv.classList.toggle('move');
});
WORKING DEMO click on red div to start animation.
BTW If you want animate something. It is always better to animate properties that doesn't force layout updates: transform and opacity.
Other properties, like top, bottom, margin are expensive for browser to animate. You should avoid them if possible.
Read more

You need to differentiate between the two phases, moving down and moving up. It can be a simple true/false boolean, but storing a "speed" or "delta" value (like +/-1) is also a very typical approach.
var v = 0;
var delta=1;
function verticalMove() {
redBox = document.getElementById('verticalDiv')
v += delta;
redBox.style.top = v + "px";
if (v <= 0) delta = 1;
if (v >= 50) delta = -1;
}
function startMove(event) {
setInterval(verticalMove,30);
event.target.onclick="";
}
.verticalDiv {
position: absolute;
top: 0px;
right: 500px;
width: 100px;
height: 100px;
background: red;
}
<div class="verticalDiv" id="verticalDiv" onclick="startMove(event)"></div>

How to animate the css zoom property

Is it possible to get a smooth transition for the css zoom property?
I googled a lot, but the results for the keywords "css" and "zoom" are always about transform and transition. So, I don't want to know how to do it with transform and scale and so on. Just with the css zoom property.
document.querySelector('div').addEventListener('click', function(e) {
e.target.classList.toggle('zoom');
});
div {
width: 50px;
height: 50px;
background: red;
cursor: pointer;
}
.zoom {
zoom: 200%;
}
<div>click me!</div>

Non-standard This feature is non-standard and is not on a standards
track. Do not use it on production sites facing the Web: it will not
work for every user. There may also be large incompatibilities between
implementations and the behavior may change in the future.
The non-standard zoom CSS property can be used to control the
magnification level of an element. transform: scale() should be used
instead of this property, if possible. However, unlike CSS Transforms,
zoom affects the layout size of the element.
MDN
So, you can use scale for this.
document.querySelector('div').addEventListener('click', function(e) {
e.target.classList.toggle('zoom');
});
div {
width: 50px;
height: 50px;
background: red;
cursor: pointer;
transition:.5s;
transform-origin:left top;
}
.zoom {
transform:scale(2);
}
<div>click me!</div>

function zoomIn(tg) {
let fr = 100;
setInterval(function() {
if(fr < 200) {
fr++;
tg.style.zoom = fr + "%";
};
}, 5);
}
function zoomOut(tg) {
let fr = 200;
setInterval(function() {
if(fr > 100) {
fr--;
tg.style.zoom = fr + "%";
};
}, 5);
}
document.querySelector('div').addEventListener('click', function(e) {
if(e.target.classList.contains('zoom')) {
e.target.classList.remove("zoom")
zoomOut(e.target);
} else {
e.target.classList.add("zoom");
zoomIn(e.target);
}
});
div {
width: 50px;
height: 50px;
background: red;
cursor: pointer;
transition: .5s;
}
<div>click me!</div>

You can use css transition, for your case:
.zoom {
transition: width 1s, height 1s;
}
Here all times that this width and height div changes will get 1 second

JavaScript on scroll to shrink logo AND menu bar

I'm working on a WordPress site, I have used the following JavaScript code to shrink the logo on scroll:
logo has id #logoid
CSS
.logoclass {width:100%;
transition: width 0.5s linear;}
.scroll {margin-top:-10px;
width:55%;
transition: width 0.5s linear;}
Javascript
<script type="text/javascript">
window.onscroll = () => {
const nav = document.querySelector('#logoid');
if(this.scrollY <= 250) nav.className = 'logoclass'; else nav.className =
'scroll';};
</script>
Now this works fine to simply shrink the image and restore size.
Now I have two problems:
Since I'm using WordPress plugins, there are many attributes applied
to the logo internally and are not in my .logoclass or in the
.scroll so these attributes get removed once I scroll and do not
get applied again. Is there a way to :
a) On scroll down ONLY change size while keeping other attributes
intact
b) On scroll up revert to initial settings completely (remove new
class)
My second question is, I want to also modify the menu bar size on scroll, but I cannot use the same code twice because it seems to only accept the code written last. Possibly because windows.onscroll gets added twice. Any way to incorporate both?

For #1, you should use the classList property to add or remove classes.
For #2, you should be able to add whatever changes you want in the same if statement.
window.onscroll = () => {
const nav = document.querySelector('#logoid');
const menu = document.querySelector('#menubar');
if (this.scrollY <= 250) {
nav.classList.remove('scroll');
menu.classList.remove('someclass');
} else {
nav.classList.add('scroll');
menu.classList.add('someclass');
}
};
.logoclass {
width: 100%;
transition: width 0.5s linear;
}
.scroll {
margin-top: -10px;
width: 55%;
transition: width 0.5s linear;
}
body {
height: 1000px;
}
#logoid {
position: absolute;
top: 0px;
background: red;
height: 25px;
}
<div id="logoid" class="logoclass"></div>
<div id="menubar" class="menuclass"></div>

If you add a global scroll class to your body tag you won't have to change your JavaScript if you want to change more things on scroll, only your CSS.
window.onscroll = () => {
const body = document.querySelector('body');
if (this.scrollY <= 250) {
body.classList.remove('scroll');
} else {
body.classList.add('scroll');
}
};
.logoclass {
width: 100%;
transition: width 0.5s linear;
}
.scroll .logoclass, .scroll .menuclass {
margin-top: -10px;
width: 55%;
transition: width 0.5s linear;
}
body {
height: 1000px;
}
#logoid {
position: absolute;
top: 0px;
background: red;
height: 25px;
}
<div id="logoid" class="logoclass"></div>
<div id="menubar" class="menuclass"></div>
If you wan't to run multiple functions on scroll you should use addEventListener.
window.addEventListener('scroll', function() {
doSomething();
});
window.addEventListener('scroll', function() {
doSomeOtherThing();
});

How to dynamically create '#-Keyframe' CSS animations?

I have a requirement to rotate a div and stop at a particular position ( The value will be received from the server).
I tried native JS to rotate and stop but it is eating up my CPU big time.
I can rotate with CSS animation but I need to create a class which will dynamically describe where to stop the animation. Something like
#-webkit-keyframes spinIt {
100% {
-webkit-transform: rotate(A_DYNAMIC_VALUE);
}
}
#-moz-keyframes spinIt {
100% {
-webkit-transform: rotate(A_DYNAMIC_VALUE);
}
}
Here is one reference
http://jsfiddle.net/bVkwH/8/

You can insert stylesheet rules dynamically to override previous styles in the head. This helps avoid adding yet another library for a single task.
var style = document.createElement('style');
style.type = 'text/css';
var keyFrames = '\
#-webkit-keyframes spinIt {\
100% {\
-webkit-transform: rotate(A_DYNAMIC_VALUE);\
}\
}\
#-moz-keyframes spinIt {\
100% {\
-webkit-transform: rotate(A_DYNAMIC_VALUE);\
}\
}';
style.innerHTML = keyFrames.replace(/A_DYNAMIC_VALUE/g, "180deg");
document.getElementsByTagName('head')[0].appendChild(style);

well i don't think it is easy to create dynamic #keyframes they are inflexible because they must be hard-coded.
Transitions are a little easier to work with, as they can gracefully respond to any CSS changes performed by JavaScript.
However, the complexity that CSS transitions can give you is pretty limited — an animation with multiple steps is difficult to achieve.
This is a problem that CSS #keyframe animations are meant to solve, but they don’t offer the level of dynamic responsiveness that transitions do.
but these links might help you
Link1 : a tool that generates a #-webkit-keyframe animation with many tiny steps. This opens the door to an unlimited selection of easing formula.
Link2 it will be a great help for you to take it as a base as it provides a UI to create animations and exports it to CSS code.
I guess this solution will definitely work for you. Its is used for dynamic keyframes

Let me share an updated (2019) answer to this.
Yes, it's possible without Javascript using CSS Variables (supported by all modern browsers).
--lightScaleStart: 0.8;
.light {
animation: grow 2s alternate infinite ease-in-out;
}
.light.yellow {
--lightScaleEnd: 1.1;
}
.light.red {
--lightScaleEnd: 1.2;
}
#keyframes grow {
from {
transform: scale(var(--lightScaleStart));
}
to {
transform: scale(var(--lightScaleEnd));
}
}
See demo on Codepen Dynamic CSS Animations with CSS Variables
Edit: Here's a CSS Tricks article about it too.

Alex Grande's answer works GREAT for a few keyframes. But, say you want to dynamically keep adding in keyframes over and over again, then your webpage get really laggy really quick. To solve this problem, just STOP creating new DOM elements. Rather, create 1 new DOM stylesheet, and just reuse it with the insertRule. If you want even more keyframes (like if you're generating a new keyframe every animationframe), then you need to set up a system which deletes old keyframes after they're no longer used. This is a good start to how something like this can be achieved.
var myReuseableStylesheet = document.createElement('style'),
addKeyFrames = null;
document.head.appendChild( myReuseableStylesheet );
if (CSS && CSS.supports && CSS.supports('animation: name')){
// we can safely assume that the browser supports unprefixed version.
addKeyFrames = function(name, frames){
var pos = myReuseableStylesheet.length;
myReuseableStylesheet.insertRule(
"#keyframes " + name + "{" + frames + "}", pos);
}
} else {
addKeyFrames = function(name, frames){
// Ugly and terrible, but users with this terrible of a browser
// *cough* IE *cough* don't deserve a fast site
var str = name + "{" + frames + "}",
pos = myReuseableStylesheet.length;
myReuseableStylesheet.insertRule("#-webkit-keyframes " + str, pos);
myReuseableStylesheet.insertRule("#keyframes " + str, pos+1);
}
}
Example usage:
addKeyFrames(
'fadeAnimation',
'0%{opacity:0}' +
'100%{opacity:1}'
);
Also, Alex Grande, I am pretty sure that document.getElementsByTagName('head')[0] and type = 'text/css' hasn't been needed since IE8, and #keyframes aren't supported till IE10. Just saying...

This is now easily achievable with the new Web Animations API, which looks like this:
const anim = document.getElementById("foo").animate(
[
{ transform: `rotate(${A_DYNAMIC_VALUE})` }
],
{ duration: 3000, iterations: Infinity }
);
// and later
anim.pause();
The first argument to .animate takes a list of keyframes, and the second takes the animation options (e.g. duration, how many times it repeats, etc).

You can change the style in CSSKeyframeRule, and this works fine for me in Chrome, just as the code below.
Hope this will help:)
<html>
<head>
<style>
#text {
display: inline-block;
}
</style>
</head>
<body>
<div id="text">TEXT</div>
<script>
// Dynamically create a keyframe animation
document.styleSheets[0].insertRule('\
#keyframes anim {\
from { transform: rotateZ(0deg); }\
to { transform: rotateZ(360deg); }\
}'
);
var div = document.getElementById('text');
div.style.animation = 'anim 1s linear forwards';
// This function will change the anim
function stopAtSomeDeg(d) {
var ss = document.styleSheets[0];
var anim;
for (var i in ss.cssRules) {
// Find your animation by name
if (ss.cssRules[i].name === 'anim') {
anim = ss.cssRules[i];
break;
}
}
var stopFrame = anim.cssRules[1]; // This indicates the second line of "anim" above.
// Change any attributes
stopFrame.style.transform = 'rotateZ(' + d + 'deg)';
}
stopAtSomeDeg(180);
</script>
</body>
</html>

With CSS variables: You can use the pseudo :root of the element to declare a css variable within the css rules, then manipulate that variable using Javascript.
:root {--variable-name:property;} which is basically the root element of the document <html>. Then change the value of the CSS root variable/s using JS with:
element.style.setProperty('--variable-name','value'). Pass the declared root variable --variable-name as the name and assign the new value. Then in your #keyframes css rules, add the root variable name, like: from: { top: var(--top-position)}, to the property within the offset #keyframe rule. Example:
:root {
--top-position-start: 0px;
--left-position-start: 0px;
--top-position-end: 200px;
--left-position-end: 200px;
}
.element {
top: var(--top-position-start);
left: var(--left-position-start);
animation: movePos 1s ease-in;
}
#keyframes movePos {
from: {
top: var(--top-position-start);
left: var(--left-position-start);
}
to: {
top: var(--top-position-end);
left: var(--left-position-end);
}
}
Then the JS would like something like:
let ran = getRandomInt(99);
let skew = ran + getRandomInt(10);
root.style.setProperty('--top-position-end', `${ran}vw`);
root.style.setProperty('--left-position-end', `${skew}vw`);
By using the CSS variable on the root element, you are able to pass it along to the #keyframes event.
See the following working example using randomly placed div using CSS left and background-color:rgb()(red, green, blue) passed using the html:root style to #keyframes within CSS.
let root = document.documentElement;
let rain = document.querySelectorAll('.drop');
function getMaxInt(max) {
return Math.floor(Math.random() * Math.floor(max));
}
function getMinMaxInt(min, max) {
return Math.random() * (max - min) + min;
}
// set an interval to drop the div from randomly positioned view widths on the screen
setInterval(() => {
let ran = getMaxInt(86);
let skew = ran + getMaxInt(10);
let circle = `${getMinMaxInt(3,15)}px`;
root.style.setProperty('--keyframeLeftStart', `${ran}vw`);
root.style.setProperty('--keyframeLeftEnd', `${skew}vw`);
root.style.setProperty('--animationDuration', `${ getMaxInt(2500)}ms`);
root.style.setProperty('--width', circle);
root.style.setProperty('--height', circle);
root.style.setProperty('--red', getMinMaxInt(100, 255));
root.style.setProperty('--green', getMinMaxInt(100, 255));
root.style.setProperty('--blue', getMinMaxInt(100, 255));
}, getMaxInt(3500))
* {
padding: 0;
margin: 0;
box-sizing: border-box;
}
/* here we define some css variables for the document :root
essentially, these will be the first iteration of the elements style
then JS will take voer and set the values from script */
:root {
--keyframeTop: 0;
--keyframeBottom: 98vh;
--keyframeLeftStart: 2vw;
--keyframeLeftEnd: 10vw;
--animationDuration: 1s;
--width: 5px;
--height: 5px;
--red: 100;
--green: 100;
--blue: 100;
}
body {
width: 100vw;
height: 100vh;
background-color: #000;
}
#main {
width: calc(100vw - var(--width));
height: calc(100vh - var(--height));
display: flex;
justify-content: center;
align-items: center;
color: #fff;
}
.drop {
width: var(--width);
height: var(--height);
border-radius: 50%;
position: absolute;
animation: dropping var(--animationDuration) ease-in infinite;
top: var(--keyframeTop);
left: var(--keyframeLeftStart);
background-color: rgb(var(--red),var(--green), var(--blue));
}
#keyframes dropping {
0% {
top: var(--keyframeTop);
left: var(--keyframeLeftStart);
background-color: rgb(var(--red),var(--green), var(--blue));
}
50% {
background-color: rgb(var(--green),var(--blue), var(--red));
}
100% {
top: var(--keyframeBottom);
left: var(--keyframeLeftEnd);
background-color: rgb(var(--blue),var(--red), var(--green));
}
}
<div id="main">
<div class="drop"></div>
</div>

In JavaScript is it possible to access to the style sheet with document.styleSheets. Every sheet has a rule and/or cssRule list (browser depending) and a CSSStyleSheet.insertRule() method.
This method allows you to add a new keyframe raw as a string:
JavaScript
function insertStyleSheetRule(ruleText)
{
let sheets = document.styleSheets;
if(sheets.length == 0)
{
let style = document.createElement('style');
style.appendChild(document.createTextNode(""));
document.head.appendChild(style);
}
let sheet = sheets[sheets.length - 1];
sheet.insertRule(ruleText, sheet.rules ? sheet.rules.length : sheet.cssRules.length);
}
document.addEventListener("DOMContentLoaded", event =>
{
insertStyleSheetRule("#keyframes spinIt { 0% { transform: rotate(-20deg); } 100% { transform: rotate(20deg); } }");
insertStyleSheetRule("#box { " +
"animation: spinIt 1s infinite alternate cubic-bezier(0.5,0,0.5,1); " +
"width: 64px; height: 64px; background-color: red; border: 4px solid black; " +
"}");
});
html
<div id="box"></div>
demo: https://jsfiddle.net/axd7nteu/

You could create a new stylesheet with the animation you want in it.
For Example:
function addAnimation(keyframe){
var ss=document.createElement('style');
ss.innerText=keyframe;
document.head.appendChild(ss);
}
This would create a new stylesheet with your animation.
This method has only been tested in Chrome.

Setting a #keyframe in one call with JavaScript, and use it, using append(), Object.assign(), and template strings.
document.body.append(
Object.assign(document.createElement("style"), {
textContent: `#keyframes coolrotate { from { transform: scale(1, 1) translate(-0.1em, 0)} to { transform: scale(-1, 1) translate(0, 0) }} small { display: inline-block; font-size:2.3em; animation: 1s infinite alternate coolrotate } body {font-size: x-large}`
}),
Object.assign(document.createElement("span"), {
innerHTML: `<span>c</span><small>o</small><span>o</span><small>L</small><small>...</small>`,
style: "font-weight: 1000; font-size: 3.3em;"
})
)

the user7892745 wont work for me, need some little adjustement
1° "pos" not understand wot should be, but the console log say "undefined"
so I've remove " , pos"
2° " myReuseableStylesheet.insertRule" give me error " is not a function"
so I used "innerHTML" insted of "insertRule"
3° finally I've moved "
document.head.appendChild( myReuseableStylesheet );" at the end
but after this it work fine and it's exact what I looking for.
thanks a lot user7892745 :D
maybe the problem I had, come form the way I use it
this is the script i used with it
var getclass = document.getElementsByClassName("cls");
var countclass = getclass.length;
for (var i=0; i <countclass; i++ ){
getclass[i].addEventListener('mouseover', function(){
// get the data-name value to show element whose id are the same
var x= this.getAttribute("data-name");
var y =document.getElementById(x);
y.style.display="block";
// because the element to show have fixed width, but different text length, they have different height
// so I need to get the highness, then use the value of height to define the 100% value of animation
// or the longer ones will be cutted an the shorten have a lot of empty space a the end
var yHeig= Math.round(parseInt(getComputedStyle(y).getPropertyValue('height')));
yHeig_ = yHeig - 10; // to shorten a bit the time from end and new passage
console.log(yHeig+" - "+ yHeig_);
addKeyFrames(
'showMe',
'0%{top:35px;}' +
'100%{top:-'+ yHeig_ +'px;}'
);
y.style.animation="showMe 7s linear infinite";
},false);
getclass[i].addEventListener('mouseout', function(){
var x= this.getAttribute("data-name");
document.getElementById(x).style.display="none";
},false);
}
i know thath a html marquee cuold seem symple to do the same thing, but dont work well,

You can create a <style> element, set its content to the CSS you want, in this case, the declaration of your animation and add it to the <head> of the page.
Also, as others have suggested, if you need to create many different animations, then it would be better to reuse a single <style> tag rather than creating multiple of them and add the new styles using CSSStyleSheet.insertRule().
Lastly, if you can use ES6's template literals/strings, your code will look much cleaner:
let dynamicStyles = null;
function addAnimation(body) {
if (!dynamicStyles) {
dynamicStyles = document.createElement('style');
dynamicStyles.type = 'text/css';
document.head.appendChild(dynamicStyles);
}
dynamicStyles.sheet.insertRule(body, dynamicStyles.length);
}
addAnimation(`
#keyframes myAnimation {
0% { transform: rotate(0); }
20% { transform: rotate(${ 360 * Math.random() }deg); }
60% { transform: rotate(${ -360 * Math.random() }deg); }
90% { transform: rotate(${ 360 * Math.random() }deg); }
100% { transform: rotate(${ 0 }deg); }
}
`);
document.getElementById("circle").style.animation = 'myAnimation 3s infinite';
html,
body {
height: 100vh;
}
body {
display: flex;
justify-content: center;
align-items: center;
margin: 0;
}
#circle {
width: 100px;
height: 100px;
box-shadow:
0 0 48px -4px rgba(0, 0, 0, .25),
0 0 0 4px rgba(0, 0, 0, .02);
border-radius: 100%;
position: relative;
overflow: hidden;
}
#circle::before {
content: '';
position: absolute;
top: 0;
left: 50%;
transform: translate(-2px);
border-left: 4px solid #FFF;
height: 24px;
box-shadow: 0 -4px 12px rgba(0, 0, 0, .25);
}
<div id="circle"></div>
Or even better:
let dynamicStyles = null;
function addAnimation(name, body) {
if (!dynamicStyles) {
dynamicStyles = document.createElement('style');
dynamicStyles.type = 'text/css';
document.head.appendChild(dynamicStyles);
}
dynamicStyles.sheet.insertRule(`#keyframes ${ name } {
${ body }
}`, dynamicStyles.length);
}
addAnimation('myAnimation', `
0% { transform: rotate(0); }
20% { transform: rotate(${ 360 * Math.random() }deg); }
60% { transform: rotate(${ -360 * Math.random() }deg); }
90% { transform: rotate(${ 360 * Math.random() }deg); }
100% { transform: rotate(${ 0 }deg); }
`);
document.getElementById("circle").style.animation = 'myAnimation 3s infinite';
html,
body {
height: 100vh;
}
body {
display: flex;
justify-content: center;
align-items: center;
margin: 0;
}
#circle {
width: 100px;
height: 100px;
box-shadow:
0 0 48px -4px rgba(0, 0, 0, .25),
0 0 0 4px rgba(0, 0, 0, .02);
border-radius: 100%;
position: relative;
overflow: hidden;
}
#circle::before {
content: '';
position: absolute;
top: 0;
left: 50%;
transform: translate(-2px);
border-left: 4px solid #FFF;
height: 24px;
box-shadow: 0 -4px 12px rgba(0, 0, 0, .25);
}
<div id="circle"></div>

Found a simple idea with JavaScript by using CSS data URI.
Solution
function addNewCSS(css_text) {
css_text = encodeURIComponent(css_text);
const url = `data:text/css,${css_text}`;
const link = document.createElement("link");
link.rel = "stylesheet";
link.href = url;
document.head.appendChild(link);
}
Function accepts CSS code as text and adds it as a style.
Working
Converts the CSS text to URI encoded form (for passing as data URL). Then creates a link tag with href as the url and relation as "stylesheet" (here rel attribute is required and won't work if not added) Finally appends the link tag to head tag.
Example
function addNewCSS(css_text) {
css_text = encodeURIComponent(css_text);
const url = `data:text/css,${css_text}`;
const link = document.createElement("link");
link.rel = "stylesheet";
link.href = url;
document.head.appendChild(link);
}
const duration = 1;
const colour = ["#2196F3", "#E91E63"];
const css_data = `
#keyframes change{
0% {
background: ${colour[0]};
}
100% {
background: ${colour[1]};
}
}
body {
animation: change ${duration}s linear infinite alternate;
}
`;
addNewCSS(css_data);
<html>
<head></head>
<body>
<h1>Wait to see JS adding background color animation</h1>
</body>
</html>
Conclusion
I haven't tested on all browsers, but works in chrome, and as it is added to the end of head tag it get priority from other tags in head, If you are planning to change values frequently, instead of adding new tags, try to edit the href of previously added tags.