code: function intersectEdge(x0, y0, x1, y1, x, y) {
      if ((y > y0 && y > y1) || (y < y0 && y < y1)) {
          return -Infinity;
      }
      // Ignore horizontal line
      if (y1 === y0) {
          return -Infinity;
      }
      var dir = y1 < y0 ? 1 : -1;
      var t = (y - y0) / (y1 - y0);
  
      // Avoid winding error when intersection point is the connect point of two line of polygon
      if (t === 1 || t === 0) {
          dir = y1 < y0 ? 0.5 : -0.5;
      }
  
      var x_ = t * (x1 - x0) + x0;
  
      return x_;
  }
docs: From x,y point cast a ray to right. and intersect with edge x0, y0, x1, y1; Return x value of intersect point