index.html

## index.html
<!doctype html>
<html>
    <head>
        <script src="http://d3js.org/d3.v3.min.js"></script>
        <script>
            var height = 500;
            var width = 960;
            var timer, startTime;
            var startTime;

            function showTimeSince(startTime) {
                var currentTime = new Date().getTime();
                var runtime = currentTime - startTime;
                document.getElementById('timeRendering').innerHTML = runtime + 'ms';
                console.log(runtime + 'ms');
            }

            function startTimer() {
                stopTimer();

                startTime = new Date().getTime();

                timer = setInterval(function() {
                    showTimeSince(startTime);
                }, 10);

                showTimeSince(startTime);
            }

            function stopTimer() {
                if (timer) {
                    clearInterval(timer);
                }

                showTimeSince(startTime);
            }

            function drawCircles(svg, data) {
                var circles = svg.selectAll('circle').data(data);
                circles.enter().append('circle')
                    .attr('r', 3);

                circles.exit().remove();

                circles
                    .attr('cx', function(d) { return d.x })
                    .attr('cy', function(d) { return d.y });
            }

            function renderChart() {
                var numPoints = parseInt(document.getElementsByName('numPoints')[0].value, 10);
                if (isNaN(numPoints)) {
                    return;
                }

                startTimer();
                var data = [];
                for (var i = 0; i < numPoints; i++) {
                    data.push({
                        x: Math.random() * width,
                        y: Math.random() * height
                    });
                }

                var svg = d3.selectAll('svg').data([0]);
                svg.enter().append('svg')
                    .attr("height", height)
                    .attr("width", width);


                startTimer();
                drawCircles(svg, data);
                stopTimer();
            }
        </script>
    </head>
    <body>
        <form action="">
            <input name="numPoints" type="text" value="10000">
            <button type="button" id="render" onClick="renderChart()">Render</button>
        </form>
        Time Rendering: <span id="timeRendering"></span>
    </body>
</html>