Set CSS keyframes in JS?

Programming
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1

I need to convert the CSS Keyframes in the fenced code block to JavaScript. The returned value should be var cylon-eye = document.getElementById("cylon-eye");.

To do this, I’ve added the following JavaScript code:

function appendStyle(styles) {
  var css = document.createElement('style');
  css.type = 'text/css';

  if (css.styleSheet) css.styleSheet.cssText = styles;
  else css.appendChild(document.createTextNode(styles));

  document.getElementsByTagName("head")[0].appendChild(css);
}

var styles = '#cylon-eye { background-color: yellow; background-image: linear-gradient(to right,rgba(255,255,255, 0.9) 25%,rgba(255,255,255, 0.1) 50%,rgba(255,255,255, 0.9) 75%); color: none; height: 100%; width: 20%;animation: 4s linear 0s infinite alternate move-eye; z-index: 10;}';
var keyFrames = '\
@keyframes move-eye {\
  from {\
    margin-left: -20%;\
  }\

  to {\
    margin-left: 100%;\
  }\
}';

window.onload = function() { appendStyle(styles) };

Once the code is added, the returned value should be var cylon-eye = document.getElementById("cylon-eye");.

2 
var cylonEye = document.getElementById("cylon-eye");

function appendStyle(styles) {
  var css = document.createElement('style');
  css.type = 'text/css';

  if (css.styleSheet) css.styleSheet.cssText = styles;
  else css.appendChild(document.createTextNode(styles));

  document.getElementsByTagName("head")[0].appendChild(css);
}

var styles = '#cylon-eye { background-color: yellow; background-image: linear-gradient(to right,rgba(255,255,255, 0.9) 25%,rgba(255,255,255, 0.1) 50%,rgba(255,255,255, 0.9) 75%); color: none; height: 100%; width: 20%;animation: 4s linear 0s infinite alternate move-eye; z-index: 10;}';
var keyFrames = '\
@keyframes move-eye {\
  from {\
    margin-left: -20%;\
  }\
\
  to {\
    margin-left: 100%;\
  }\
}';

appendStyle(keyFrames + styles);