JSFiddle - React, Tailwind, and code Playground

by SpiceLab

HTML

<canvas id="canvas123" width="90" height="60" onmouseover="canvasborder123()"></canvas>
<!-- Zu Demozwecken -->
<p id="123p" class="123c">CSS greift nicht</p>

CSS

#canvas123 {
  border-width:13px;
  border-color:black;
  border-style:solid;
}
/* Zu Demozwecken */
#123p {
  border-width:13px;
  border-color:black;
  border-style:solid;
}
.123c {
  border-color:red !important;
}

JavaScript

function canvasborder123() {
  document.getElementById("canvas123").style.borderWidth = "0";
}