how to insert css dynamically (not inline) in javascript?

Question

css version:

:root {
  --kiss: url(https://cdnjs.cloudflare.com/ajax/libs/twemoji/14.0.2/svg/1f609.svg);
  --wink: url(https://cdnjs.cloudflare.com/ajax/libs/twemoji/14.0.2/svg/1f617.svg);
}
[class*="emo_"]:after {
  display: block;
  content:'';
  width:40px;
  height:40px;
  border:1px solid red;
  border-radius:50%
}
.emo_wink:after {
  content: var(--wink);
}
.emo_kiss:after {
  content: var(--kiss);
}

<div class="emo_wink"></div>
<div class="emo_kiss"></div>

js version: I want to use the js version to avoid repetitive codes in css but Im having trouble getting it to work... I can see in the console that the styles are added but it's not rendering...

var emodata = {
  wink: '1f609',
  kiss: '1f617'
}

function emojis(data) {
  for (var key in data) {
    if (data.hasOwnProperty(key)) {
      var url = 'https://cdnjs.cloudflare.com/ajax/libs/twemoji/14.0.2/svg/' + data[key] + '.svg';
      document.documentElement.style.setProperty('--' + key, 'url(' + url + ')');
      document.styleSheets[0].insertRule(".emo_" + key + ":after { content: var(--" + key + ") }");
    }
  }
}
emojis(emodata)

[class*="emo_"]:after {
  display: block;
  content:'';
  width:40px;
  height:40px;
  border:1px solid red;
  border-radius:50%
}

<div class="emo_wink"></div>
<div class="emo_kiss"></div>

Another question: Is there a huge difference in performance and speed if I use the js version? thanks!

The performance gap will not be noticeable, since JavaScript and CSS files are cached by browsers. Computers and network are getting stronger and faster, choose direction which convenient and makes sense to you — Huy Phạm
– Huy Phạm, Commented Apr 15, 2022 at 2:55

Tanay · Accepted Answer · 2022-04-15 02:45:57Z

1

You can create a style element in javascript and append it to the head element and then append the classes accordingly.

var emodata = {

  wink: '1f609',

  kiss: '1f617'

}

function emojis(data) {
  var style = document.createElement('style');

style.type = 'text/css';
  document.querySelector('head').appendChild(style)

  for (var key in data) {

    if (data.hasOwnProperty(key)) {

      var url = 'https://cdnjs.cloudflare.com/ajax/libs/twemoji/14.0.2/svg/' + data[key] + '.svg';

      document.documentElement.style.setProperty('--' + key, 'url(' + url + ')');
      style.innerHTML+=`.emo_${key}:after{
          content: var(--${key});
      }`

    }

  }

}

emojis(emodata)

[class*="emo_"]:after {

  display: block;

  content:'';

  width:40px;

  height:40px;

  border:1px solid red;

  border-radius:50%

}

<div class="emo_wink"></div>

<div class="emo_kiss"></div>

You could also use sass to do it without javascript

answered Apr 15, 2022 at 2:45

Tanay

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1 Comment

88willr Over a year ago

thanks for the answer! when I remove the content:'' in the hardcoded css, the original js code works!

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