Reusable Chart component for D3 - using prototypes and factories

BarChart.js

(function() {
  
  // Based on article @ http://www.toptal.com/d3-js/towards-reusable-d3-js-charts
  // Publish a factory method for Chart instances
  // @usage:
  //     var runningChart = BarChart.instanceOf( {barPadding : 2 } );
  //     var weatherChart = BarChart.instanceOf()
  //                                .fillColor('coral');
  
  window.BarChart = {
    instanceOf : function (options) {
        // Publish instance
        return new Chart(options);
    }
  };  
  
  // ***************************************************
  // Define Chart class and methods
  // ***************************************************

  /**
   * Define Chart Class
   */
  function Chart(options) {

      // Special draw `selection` method used by D3
      this.render = drawSelection.bind(this);
      this.options = initialize(options);
  }

  /**
   * Build and assign prototype methods
   */
  Chart.prototype = {
      width       : makeAccessor.call(this, this.options, 'width'),
      height      : makeAccessor.call(this, this.options, 'height'),
      barPadding  : makeAccessor.call(this, this.options, 'barPadding'),
      fillColor   : makeAccessor.call(this, this.options, 'fillColor')
  };

  // ***************************************************
  // D3 Render method
  // ***************************************************

  /**
   * Define the D3 callback to render bar chart within the specified
   * selection DOMs
   */
  function drawSelection(selection) {
      selection.each(function(data) {
          var barSpacing = this.height / data.length;
          var barHeight = barSpacing - this.barPadding;
          var maxValue = d3.max(data);
          var widthScale = this.width / maxValue;

          d3.select(this).append('svg')
            .attr('height', this.height)
            .attr('width', this.width)
            .selectAll('rect')
            .data(data)
            .enter()
            .append('rect')
            .attr('y', function(d, i) {
                return i * barSpacing
            })
            .attr('height', barHeight)
            .attr('x', 0)
            .attr('width', function(d) {
                return d * widthScale
            })
            .style('fill', this.fillColor);
      });
  }

  // ***************************************************
  // Utility methods
  // ***************************************************


  /**
   * Build a chainable property accessor AND mutator function
   */
  function makeAccessor(fields, key) {

      return function() {
          if (!arguments.length) return fields[key];
          fields[key] = value;

          return this;
      }
  }

  /**
   * Clone options data and initialize with defaults (if needed)
   */
  function initialize(options) {
      return extend({
          width: 900,
          height: 200,
          barPadding: 1,
          fillColor: 'steelblue'
      },options);
  }
  
  /**
   * 
   */
  function extend(dst) {
    for (var i = 1, ii = arguments.length; i < ii; i++) {
      var obj = arguments[i];
      if (obj) {
        var keys = Object.keys(obj);
        for (var j = 0, jj = keys.length; j < jj; j++) {
          var key = keys[j];
          dst[key] = obj[key];
        }
      }
    }
    return dst;
  }      
  
})();

What about version 4 of d3? Something is going wrong in line 27, the context is not passed to the function, maybe, i'm not javascript expert but because of this i'm very interested on how all this stuff can work, i always coded in the classic manner, Thanks

My version of it: https://github.com/valcri/reusable-d3-chart-template