function Cylinder(cyl_height, cyl_diameter) {  
  this.cyl_height = cyl_height;  
  this.cyl_diameter = cyl_diameter;  
}  
  
Cylinder.prototype.Volume = function () {  
  var radius = this.cyl_diameter / 2;  
  return this.cyl_height * Math.PI * radius * radius;  
};  
  
var cyl = new Cylinder(7, 4);  
// Volume of the cylinder with four decimal places.  
console.log('volume =', cyl.Volume().toFixed(4));