JSFiddle - React, Tailwind, and code Playground

HTML

<canvas id="myCanvas" width="300" height="150"></canvas>
<a id="download" download="CanvasDemo.png">Speichern</a>

JavaScript

var canvas = document.getElementById("myCanvas");
var ctx = canvas.getContext("2d");
ctx.fillStyle = "red";
ctx.fillRect(10, 10, 50, 50);

function download() {
    var dt = canvas.toDataURL();
    this.href = dt; 
}

document.getElementById('download').addEventListener('click', download, false);