Move the mouse smoothly from side to side to see a lag in the drawn position.
<!DOCTYPE html>
<meta charset="utf-8">
<body>
<script src="//d3js.org/d3.v4.min.js"></script>
<script>
var width = 960,
height = 300;
var canvas = d3.select("body").append("canvas")
.attr("width", width)
.attr("height", height);
var context = canvas.node().getContext("2d");
context.fillStyle = 'steelblue';
var mouseLocation = [0,0];
d3.select(window).on("mousemove", () => {
mouseLocation[0] = d3.event.clientX;
mouseLocation[1] = d3.event.clientY;
});
// show mouse
d3.timer(function() {
context.clearRect(0, 0, width, height);
context.beginPath();
context.arc(mouseLocation[0], mouseLocation[1], 2, 0, 2 * Math.PI);
context.fill();
});
</script>