Understanding _initAttr

[samselikoff]

I'm trying to understand the initAttr function:

  function _initAttr(internalName, d3Name, defaultValue) {
    if (!this.base.attr(d3Name)) {
      this[internalName] = defaultValue;
      this.base.attr(d3Name, defaultValue);
    } else {
      this[internalName] = this.base.attr(d3Name);
    }
  }

It seems like after you use it

    // make sure container height and width are set.
    _initAttr.call(this, "_width", "width", 200);
    _initAttr.call(this, "_height", "height", 200);

these lines become unnecessary:

 // setup some reasonable defaults
    chart._width  = chart.base.attr("width") || 200;
    chart._height = chart.base.attr("height") || 200;

since in either case (svg width/height are already set, or they're not) the initAttr function is assigning a value to this._width and this._height. What am I missing?