Simple Counter

counter.js

class Counter {
    constructor() {
        this.map = new Map();
    }

    add(key) {
        this.map.set(key, this.map.has(key) ? this.map.get(key) + 1 : 1);
    }

    print() {
        // TODO fix me
        console.log(this.map)
    }

    count() {
        return this.map.size;
    }
}

// test
counter = new Counter;
counter.add('a')
counter.add('a')
counter.add('a')
counter.add('b')

counter.print()
console.log(counter.count())