catalogue.js

class Catalogue {
    constructor(contents) {
        this.contents = contents;
    }

    search(title, artist){
        return this.contents
            .filter((cd) =>
                cd.matches(title, artist))[0];
    }

    receive(batch){
        const {title, artist, copies} = batch.cds[0];
        const cd = this.search(title, artist);
        cd.stock += copies;
    }
}