JSFiddle - React, Tailwind, and code Playground

CSS

.bar {
  fill: steelblue;
}

.bar:hover {
  fill: brown;
}

.axis {
  font: 10px sans-serif;
}

.axis path,
.axis line {
  fill: none;
  stroke: #000;
  shape-rendering: crispEdges;
}

.x.axis path {
  display: none;
}

JavaScript

var newdata = [{
  "letter": 'A',
  "frequency": .08167
}, {
  "letter": 'B',
  "frequency": .01492
}, {
  "letter": 'C',
  "frequency": .01867
}, {
  "letter": 'D',
  "frequency": .01877
}, {
  "letter": 'E',
  "frequency": .01477
}];

// Mike Bostock "margin conventions"
var margin = {top: 20, right: 20, bottom: 30, left: 40},
    width = 960 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom;

// D3 scales = just math
// x is a function that transforms from "domain" (data) into "range" (usual pixels)
// domain gets set after the data loads
var x = d3.scale.ordinal()
    .rangeRoundBands([0, width], .01);

var y = d3.scale.linear()
    .range([height, 0]);

// D3 Axis - renders a d3 scale in SVG
var xAxis = d3.svg.axis()
    .scale(x)
    .orient("bottom");

var yAxis = d3.svg.axis()
    .scale(y)
    .orient("left")
    .ticks(10, "%");

// create an SVG element (appended to body)
// set size
// add a "g" element (think "group")
// annoying d3 gotcha - the 'svg' variable here is a 'g' element
// the final line sets the transform on <g>, not on <svg>
var svg = d3.select("body").append("svg")
    .attr("width", width + margin.left + margin.right)
    .attr("height", height + margin.top + margin.bottom)
  .append("g")
    .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

svg.append("g")
    .attr("class", "x axis")
    .attr("transform", "translate(0," + height + ")")

svg.append("g")
    .attr("class", "y axis")
  .append("text") // just for the title (ticks are automatic)
    .attr("transform", "rotate(-90)") // rotate the text!
    .attr("y", 6)
    .attr("dy", ".71em")
    .style("text-anchor", "end")
    .text("Frequency");

// d3.tsv is a wrapper around XMLHTTPRequest, returns array of arrays (?) for a TSV file
// type function transforms strings to numbers, dates, etc.
replay(newdata);
function type(d) {
  // + coerces to a Number from a String (or anything)
  d.frequency = +d.frequency;
  return...