GoF State

State.js

class TrafficLight {
    constructor() {
        this.count = 0;
        this.currentState = new Red(this);
    }
    change (state) {
        // limits number of changes
        if (this.count++ >= 10) return;
        this.currentState = state;
        this.currentState.go();
    }
    start () {
        this.currentState.go();
    }
}

class Red {
    constructor(light) {
        this.light = light;
    }
    
    go () {
        console.log("Red --> for 1 minute");
        this.light.change(new Green(this.light));
    }
}

class Yellow {
    constructor(light) {
        this.light = light;
    }

    go () {
        console.log("Yellow --> for 10 seconds");
        this.light.change(new Red(this.light));
    }
}

class Green  {
    constructor(light) {
        this.light = light;
    }
    
    go () {
        console.log("Green --> for 1 minute");
        this.light.change(new Yellow(this.light));
    }
}

const trafficLight = new TrafficLight();
trafficLight.start();

// Red --> for 1 minute
// Green --> for 1 minute
// Yellow --> for 10 seconds
// Red --> for 1 minute
// Green --> for 1 minute
// Yellow --> for 10 seconds
// Red --> for 1 minute
// Green --> for 1 minute
// Yellow --> for 10 seconds
// Red --> for 1 minute
// Green --> for 1 minute