simple D3 line chart

copied from: https://leanpub.com/D3-Tips-and-Tricks/read#leanpub-auto-starting-with-a-basic-graph

by Shashank D

HTML

<script src="https://d3js.org/d3.v3.js"></script>


<button id='autofit'>
Autofit
</button>

CSS

body {
    font: 12px Arial;
}
path {
    stroke: steelblue;
    stroke-width: 2;
    fill: none;
}
.axis path, .axis line {
    fill: none;
    stroke: grey;
    stroke-width: 1;
    shape-rendering: crispEdges;
}
rect.extent {
  fill: none;
  stroke: #ddd;
}

JavaScript

var margin = {
    top: 30,
    right: 20,
    bottom: 30,
    left: 50
};
var width = 600 - margin.left - margin.right;
var height = 270 - margin.top - margin.bottom;

var parseDate = d3.time.format("%d-%b-%y").parse;

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

var fullX = x.copy();
var fullY = y.copy();

var xAxis = d3.svg.axis().scale(x)
    .orient("bottom").ticks(5);

var yAxis = d3.svg.axis().scale(y)
    .orient("left").ticks(5);

var valueline = d3.svg.line()
    .x(function (d) {
      return x(d.date);
    })
    .y(function (d) {
      return y(d.close);
    });

var svg = d3.select("body")
    .append("svg")
    .attr("width", width + margin.left + margin.right)
    .attr("height", height + margin.top + margin.bottom);
    
 var g = svg
    .append("g")
    .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

// Get the data
var data = [{
    date: "1-May-12",
    close: "58.13"
}, {
    date: "30-Apr-12",
    close: "53.98"
}, {
    date: "27-Apr-12",
    close: "67.00"
}, {
    date: "26-Apr-12",
    close: "89.70"
}, {
    date: "25-Apr-12",
    close: "99.00"
}];

data.forEach(function (d) {
    d.date = parseDate(d.date);
    d.close = +d.close;
});

// Scale the range of the data
x.domain(d3.extent(data, function (d) {
    return d.date;
    }));
y.domain([0, d3.max(data, function (d) {
    return d.close;
    })]);


var gBrush = g.append('g').classed('brush', true);

var gAxisX = g.append("g") // Add the X Axis
.attr("class", "x axis")
    .attr("transform", "translate(0," + height + ")")
    
var gAxisY = g.append("g") // Add the Y Axis
.attr("class", "y axis");

function drawAxes() {
  gAxisX.call(xAxis);
  gAxisY.call(yAxis);
}

drawAxes();

var brushing = false;

var zoom = d3.behavior.zoom().x(x).y(y).scaleExtent([1, 10000])
.on('zoom', function () {

  if(brushing && d3.event.sourceEvent.type === 'mousemove' && d3.event.sourceEvent.which !== 2) return ;

 ...