Edit in JSFiddle

function Sphere(radius) {
    this.radius = radius;
    this.pi = 3.14;
    
    this.volume = function() {
        return Math.pow(this.pi, 3) * 3/4 * this.radius;
    };
}

var football = new Sphere(10);

document.body.innerHTML += "<p>Volume: " + football.volume() + "</p>";