Dynamically update chart data in D3 (1)

HTML

<script src="http://d3js.org/d3.v3.min.js"></script>
<script src="http://underscorejs.org/underscore-min.js"></script>
<html>
  <body>
    <div id='chart'/>
  </body>
</html>

JavaScript

var margin = {top: 20, right: 20, bottom: 30, left: 50},
  width = 300 - margin.left - margin.right,
  height = 300 - margin.top - margin.bottom;

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

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

  var svg = d3.select("div#chart").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 + ")");

  var data = [[1,1],[2,3],[3,2],[4,4]];

  var dataCallback = function(d) {
    d.x = +d[0];
    d.y = +d[1];
  };
  data.forEach(dataCallback);

  x.domain(d3.extent(data, function(d) { return d.x; }));
  y.domain([0, d3.max(data, function(d) { return d.y; })]);

  svg.append("path")
      .data([data])
      .attr("class", "area")
      .attr("d", area);

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

  svg.append("g")
      .attr("class", "y axis")
      .call(yAxis)
    .append("text")
      .attr("transform", "rotate(-90)")
      .attr("y", 6)
      .attr("dy", ".71em")
      .style("text-anchor", "end")
      .text("Number of Messages");

d3.select('#chart').on("click", function() {
    data.splice(0,1);
    data.push([5,5]);
    dataCallback(data[data.length - 1]);
    
    x.domain(d3.extent(data, function(d) { return d.x; }));
    y.domain([0, d3.max(data, function(d) { return d.y; })]);
    
    svg.select("g.x.axis").call(xAxis); 
    svg.selectAll("path").data([data])
        .attr("d", area);
});