/**
 *
 * @param P {Function} Parent
 * @param C {Function} Child
 */
function extend (P, C) {
    C.prototype = Object.create(P.prototype);
    C.prototype.constructor = C;
}
 
// Parent Class
function Parent (x) {
    this.x = x;
}
 
// Child Class
function Child (x) {
    Parent.apply(this, arguments);
}
// 継承
extend(Parent, Child);