JSFiddle - React, Tailwind, and code Playground

JavaScript

var width = 960,
    height = 500,
    padding = 1.5, // separation between same-color nodes
    clusterPadding = 6, // separation between different-color nodes
    maxRadius = 12;

var n = 200, // total number of nodes
    m = 10; // number of distinct clusters

var color = d3.scale.category10()
    .domain(d3.range(m));

// The largest node for each cluster.
var clusters = new Array(m);

var nodes = d3.range(n).map(function() {
    var i = Math.floor(Math.random() * m),
        r = Math.sqrt((i + 1) / m * -Math.log(Math.random())) * maxRadius,
        d = {cluster: i, radius: r};
    if (!clusters[i] || (r > clusters[i].radius)) clusters[i] = d;
    return d;
});

// Use the pack layout to initialize node positions.
d3.layout.pack()
    .sort(null)
    .size([width, height])
    .children(function(d) { return d.values; })
    .value(function(d) { return d.radius * d.radius; })
    .nodes({values: d3.nest()
        .key(function(d) { return d.cluster; })
        .entries(nodes)
    });

var force = d3.layout.force()
    .nodes(nodes)
    .size([width, height])
    .gravity(.02)
    .charge(0)
    .on("tick", tick)
    .start();

var svg = d3.select("body").append("svg")
    .attr("width", width)
    .attr("height", height);

var grads = svg.append("defs").selectAll("radialGradient")
    .data(nodes)
   .enter()
    .append("radialGradient")
    .attr("gradientUnits", "objectBoundingBox")
    .attr("cx", 0)
    .attr("cy", 0)
    .attr("r", "100%")
    .attr("id", function(d, i) { return "grad" + i; });

grads.append("stop")
    .attr("offset", "0%")
    .style("stop-color", "white");

grads.append("stop")
    .attr("offset", "100%")
    .style("stop-color",  function(d) { return color(d.cluster); });

var node = svg.selectAll("circle")
    .data(nodes)
   .enter()
    .append("circle")
    .style("fill", function(d, i) {
        return "url(#grad" + i + ")";
    })
    // .style("fill", function(d) { return color(d.cluster); })
   ...