shawnxcode

demo中计算控制点的for循环，当index=0时，`self.series.data[index - 1]`是取不到值的 ```javascript for(var index = 0; index < this.series.data.length; index ++) {   var last1X = diffX * (index - 1),   last1Y = Math.floor(self.height - diffY * (self.series.data[index -...