class PointCard {
    constructor() {
        this.points = 0;
        this.fraction = 0;
        this.jpyPerPoint = 100;
    }

    earn(jpy) {
        if (jpy <= 0) {
            throw RangeError(`jpy should be posivite. ${jpy} was given.`);
        }
        let pointsEarned = Math.floor(jpy / this.jpyPerPoint);
        let fractionEarned = jpy % this.jpyPerPoint;
        this.points += pointsEarned;
        this.fraction += fractionEarned;
        if (this.fraction >= this.jpyPerPoint) {
            this.points++;
            this.fraction -= this.jpyPerPoint;
        }
    }

    use(pointsUsed) {
        if (this.points < pointsUsed) {
            throw RangeError(`pointsUsed was larger than current points. pointsUsed = ${pointsUsed}, current points = ${this.points}`);
        }
        this.points -= pointsUsed;
    }
}

let p = new PointCard();
p.earn(1580);
console.log(p.points);
console.log(p.fraction);
p.earn(30);
console.log(p.points);
console.log(p.fraction);
p.use(10);
p.use(10);
p.use(10);