d3.js Graph with many features

This is a follow on from the simple d3.js graph used as an example in the book D3 Tips and Tricks.

It is aimed at exploring some features of d3.js and should be taken in context with the text of the book which can be downloaded for free from Leanpub.

<!DOCTYPE html>
<meta charset="utf-8">
<style>

body {
    font: 12px Arial;
}

text.shadow {
  stroke: #fff;
  stroke-width: 2.5px;
  opacity: 0.9;
}

path { 
    stroke: steelblue;
    stroke-width: 2;
    fill: none;
}

.axis path,
.axis line {
    fill: none;
    stroke: grey;
    stroke-width: 1;
    shape-rendering: crispEdges;
}

.grid .tick {
    stroke: lightgrey;
    stroke-opacity: 0.7;
    shape-rendering: crispEdges;
}
.grid path {
          stroke-width: 0;
}

.area {
    fill: lightsteelblue;
      stroke-width: 0;
}

</style>
<body>
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.17/d3.min.js"></script>

var margin = {top: 30, right: 20, bottom: 35, left: 50},
    width = 600 - margin.left - margin.right,
    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 xAxis = d3.svg.axis()
    .scale(x)
    .orient("bottom")
    .ticks(5);

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

var area = d3.svg.area()
    .x(function(d) { return x(d.date); })
    .y0(height)
    .y1(function(d) { return y(d.close); });

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)
    .append("g")
        .attr("transform", 
              "translate(" + margin.left + "," + margin.top + ")");

// function for the x grid lines
function make_x_axis() {
    return d3.svg.axis()
        .scale(x)
        .orient("bottom")
        .ticks(5)
}

// function for the y grid lines
function make_y_axis() {
  return d3.svg.axis()
      .scale(y)
      .orient("left")
      .ticks(5)
}

// Get the data
d3.csv("data.csv", function(error, data) {
    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; })]);

// Add the filled area
    svg.append("path")
        .datum(data)
        .attr("class", "area")
        .attr("d", area);

// Draw the x Grid lines
    svg.append("g")
        .attr("class", "grid")
        .attr("transform", "translate(0," + height + ")")
        .call(make_x_axis()
            .tickSize(-height, 0, 0)
            .tickFormat("")
        )

// Draw the y Grid lines
    svg.append("g")            
        .attr("class", "grid")
        .call(make_y_axis()
            .tickSize(-width, 0, 0)
            .tickFormat("")
        )

// Add the valueline path.
    svg.append("path")
        .attr("d", valueline(data));

// Add the X Axis
    svg.append("g")
        .attr("class", "x axis")
        .attr("transform", "translate(0," + height + ")")
        .call(xAxis);

// Add the Y Axis
    svg.append("g")
        .attr("class", "y axis")
        .call(yAxis);

// Add the text label for the X axis
    svg.append("text")
        .attr("transform",
              "translate(" + (width/2) + " ," + 
                             (height+margin.bottom) + ")")
        .style("text-anchor", "middle")
        .text("Date");

// Add the white background to the y axis label for legibility
    svg.append("text")
        .attr("transform", "rotate(-90)")
        .attr("y", 6)
        .attr("x", margin.top - (height / 2))
        .attr("dy", ".71em")
        .style("text-anchor", "end")
        .attr("class", "shadow")
        .text("Price ($)");

// Add the text label for the Y axis
    svg.append("text")
        .attr("transform", "rotate(-90)")
        .attr("y", 6)
        .attr("x", margin.top - (height / 2))
        .attr("dy", ".71em")
        .style("text-anchor", "end")
        .text("Price ($)");

// Add the title
    svg.append("text")
        .attr("x", (width / 2))     
        .attr("y", 0 - (margin.top / 2))
        .attr("text-anchor", "middle")
        .style("font-size", "16px")
        .style("text-decoration", "underline")
        .text("Price vs Date Graph");

});

</script>
</body>

https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.17/d3.min.js