const width = 500;
const height = 500;
const radius = 10;
const orange = d3.hsl("orange");
const steelblue = d3.hsl("steelblue");
const limegreen = d3.hsl("limegreen");
const svg = d3.select("body")
.append("svg")
.attr("width", width)
.attr("height", height);
const target = svg.append("rect")
.attr("x", 0)
.attr("y", 0)
.attr("width", width)
.attr("height", height)
.attr("fill", "none")
.attr("pointer-events", "all")
.on("mousemove", () => {
circle.attr("cx", d3.event.clientX - radius);
circle.attr("cy", d3.event.clientY - radius);
});
const circle = svg.append("circle")
.attr("r", radius)
.attr("fill", steelblue)
.attr("pointer-events", "none");
const rect = svg.selectAll(null)
.data(d3.range(3).map(d => [Math.random() * width, Math.random() * height]))
.enter().append("rect")
.attr("x", d => d[0])
.attr("y", d => d[1])
.attr("width", 50)
.attr("height", 50)
.attr("fill", orange)
.attr("opacity", 0.5)
.on("mouseover", function() {
d3.select(this).transition().attr("fill", limegreen);
})
.on("mousemove", function() {
target.node().dispatchEvent(new MouseEvent(d3.event.type, d3.event));
})
.on("mouseout", function() {
d3.select(this).transition().attr("fill", orange);
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/5.7.0/d3.min.js"></script>