JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://d3js.org/d3.v3.min.js"></script>
<!DOCTYPE html>
<meta charset="utf-8">
<title>Test Diagonal</title>
<p id="chart"></p>

CSS

.link {
        fill: none;
        stroke: #ccc;
        stroke-width: 1.5px;
    }

JavaScript

var data = [
    
    {
    
    name: "p1",
    
    
    children: [{name: "c1"}, {name: "c2"}, {name: "c4"}, {name: "c4"}]
    
    
    
    }, {
    
    name: "p2",
    
    
    children: [{name: "c1"}, {name: "c2"}, {name: "c4"}, {name: "c4"}]
    
    
    
    },
    
    
    
    
    ];
    var width = 400, height = 200, radius = 10, gap = 50;

    // test layout
    var nodes = [];
    var links = [];
    data.forEach(function(d, i) {
        d.x = width/4;
        d.y = height/2;
        nodes.push(d);
        d.children.forEach(function(c, i) {
            c.x = 3*width/4;
            c.y = gap * (i +1) -2*radius;
            nodes.push(c);
            
            var a = {x:c.y, y:c.x};
            var b = {x:d.y, y:d.x};
            links.push({source: b, target: a});
        })
    })

    var color = d3.scale.category20();

    var svg = d3.select("#chart").append("svg")
            .attr("width", width)
            .attr("height", height)
            .append("g");
    var diagonal = d3.svg.diagonal()
            .projection(function(d) { return [d.y, d.x]; });

    var link = svg.selectAll(".link")
            .data(links)
            .enter().append("path")
            .attr("class", "link")
            .attr("d", diagonal);

    var circle = svg.selectAll(".circle")
            .data(nodes)
            .enter()
            .append("g")
            .attr("class", "circle");

    var el = circle.append("circle")
            .attr("cx", function(d) {return d.x})
            .attr("cy", function(d) {return d.y})
            .attr("r", radius)
            .style("fill", function(d) {return color(d.name)})
            .append("title").text(function(d) {return d.name});