Edit in JSFiddle

var pileup = require("pileup");

var sources = [
  {
    viz: pileup.viz.genome(),
    isReference: true,
    data: pileup.formats.twoBit({
      url: 'https://www.biodalliance.org/datasets/hg19.2bit'
    }),
    name: 'Reference'
  },
  {
    viz: pileup.viz.genes(),
    data: pileup.formats.bigBed({
      url: 'https://www.biodalliance.org/datasets/ensGene.bb'
    }),
    name: 'Genes'
  }
];

var p = pileup.create("yourDiv", {
  range: {contig: 'chr17', start: 7512384, stop: 7512544},
  tracks: sources
});

<script src="https://wzrd.in/bundle/pileup@latest" type="text/javascript"></script>
<div id="yourDiv"></div>

/**
 * This is the default stylesheet for pileup.js.
 * In general, it attempts to look like IGV.
 * You are encouraged to override anything you like.
 */

.pileup-root {
  display: flex;
  flex-direction: column;
  height: 100%;
}

.pileup-root > .track {
  display: flex;
  flex-direction: row;
}
.track-label {
  flex: 0 0 100px;  /* fixed-width track labels */
  text-align: right;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  font-size: 0.9em;
  position: relative;  /* make this an offset parent for positioning the label. */
}
.track-label > span {
  padding-right: 5px;
}
/* bottom-justify these track labels */
.track.reference .track-label > span,
.track.variants .track-label > span
{
  position: absolute;
  bottom: 0;
  right: 0;
}
.track-content {
  flex: 1;  /* stretch to fill remaining space */
  overflow-y: auto;
  overflow-x: hidden;
  position: relative;
}
.track-content > div > div {
  position: absolute; /* Gets the child of the flex-item to fill height 100% */
}

/* controls */
.pileup-root > .controls {
  flex: 0 0 30px;  /* fixed height */
}
.pileup-root > .controls form.controls {
  margin-bottom: 0;  /* overrides browser default */
}
.pileup-root > .controls .zoom-controls {
  display: inline-block;
}
.pileup-root > .controls .btn-zoom-out:before {
  content: '-';
}
.pileup-root > .controls .btn-zoom-in:before {
  content: '+';
}

/* reference track */
.pileup-root > .reference {
  flex: 0 0 20px;  /* fixed height */
}

.background {
  fill: white;
}
.basepair.A, .basepair .A { fill: #188712; }
.basepair.G, .basepair .G { fill: #C45C16; }
.basepair.C, .basepair .C { fill: #0600F9; }
.basepair.T, .basepair .T { fill: #F70016; }
.basepair.U, .basepair .U { fill: #F70016; }
.basepair text, text.basepair {
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  text-anchor: middle;
}
.pair.loose text {
  font-size: 24;
}
.pair.tight text {
  font-size: 12;
  font-weight: bold;
}
.pair text, .pair rect {
  visibility: hidden;
}
.pair.loose text,
.pair.tight text {
  visibility: visible;
}
.pair.blocks rect {
  visibility: visible;
}

/* gene track */
.pileup-root > .genes {
  flex: 0 0 50px;
}
.gene {
  stroke-width: 1;
  stroke: blue;
}
.gene text {
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  font-size: 16px;
  text-anchor: middle;
  stroke: black;
  alignment-baseline: hanging;
}
#sense, #antisense .main {
  stroke: blue;
  fill: none;
  stroke-width: 1;
}
#antisense .offset, #sense .offset {
  stroke: white;
  fill: none;
  stroke-width: 1;
}
.exon {
  fill: blue;
  stroke: none;
}

/* pileup track */
.pileup-root > .pileup {
  flex: 1;  /* stretch to fill remaining space */
}
.pileup .alignment .match {
  fill: #c8c8c8;  /* matches IGV */
}
.pileup text.basepair {
  alignment-baseline: hanging;
  font-size: 12;
  font-weight: bold;
}
.pileup .insert {
  stroke: rgb(97, 0, 216);  /* matches IGV */
  stroke-width: 2;
}
.pileup .delete {
  stroke: black;
  stroke-width: 2;
}
.pileup .network-status {
  height: 100%;
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: center;
}
.pileup .network-status-message {
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
  padding: 4px 8px;
  width: auto;
  background: #eee;
  border-radius: 3px;
  border: 1px solid #ccc;
  font-size: small;
}

/* variants */
.pileup-root > .variants {
  flex: 0 0 25px;  /* fixed height */
}
.variants rect {
  fill: #ddd;
  stroke: blue;
}