//Handler
class Rescuer {
    constructor(code, next) {
        this._code = code;
        this._next = next;
    }

    //HandleRequest()
    help(code) {
        if (this._code === code) {
            this.toHelp();
        } else if (this._next != undefined) {
            this._next.help(code);
        }
    }
}

//ConcreteHandler
class Firefighter extends Rescuer {
    constructor(next) {
        super(1, next);
    }

    toHelp() {
        console.log("call firefighters");
    }
}

//ConcreteHandler
class Police extends Rescuer {
    constructor(next) {
        super(2, next);
    }

    toHelp() {
        console.log("call the police");
    }
}

//ConcreteHandler
class Ambulance extends Rescuer {
    constructor(next) {
        super(3, next);
    }

    toHelp() {
        console.log("call an ambulance");
    }
}

let ambulance = new Ambulance();
let police = new Police(ambulance);
let firefighter = new Firefighter(police);
firefighter.help(1);
//printed: call firefighters
firefighter.help(2);
//printed: call the police
firefighter.help(3);
//printed: call an ambulance