transducerというものがあるというのを知って、どんなものか自分でもやってみた。 関数合成が見やすく効率的にできるそうな。 試行錯誤の結果、こうなりました。 const compose = (...fs) => x => fs.reduceRight( (acc, f) => f(acc), x ) const mapping = f => reducing => (acc, e) => reducing(acc, f(e)) const filtering = f => reducing => (acc, e) => f(e) ? reducing(acc, e) : reducing(acc, undefined) const folding = f => x => reducing => (acc, e) => acc.length === 0 ? reducing(acc,
![JavaScript: transducerを作ってみた](https://cdn-ak-scissors.b.st-hatena.com/image/square/1301601600b7cede3690d77461ec7b26e0c2db89/height=288;version=1;width=512/https%3A%2F%2Fqiita-user-contents.imgix.net%2Fhttps%253A%252F%252Fcdn.qiita.com%252Fassets%252Fpublic%252Farticle-ogp-background-9f5428127621718a910c8b63951390ad.png%3Fixlib%3Drb-4.0.0%26w%3D1200%26mark64%3DaHR0cHM6Ly9xaWl0YS11c2VyLWNvbnRlbnRzLmltZ2l4Lm5ldC9-dGV4dD9peGxpYj1yYi00LjAuMCZ3PTkxNiZoPTMzNiZ0eHQ9SmF2YVNjcmlwdCUzQSUyMHRyYW5zZHVjZXIlRTMlODIlOTIlRTQlQkQlOUMlRTMlODElQTMlRTMlODElQTYlRTMlODElQkYlRTMlODElOUYmdHh0LWNvbG9yPSUyMzIxMjEyMSZ0eHQtZm9udD1IaXJhZ2lubyUyMFNhbnMlMjBXNiZ0eHQtc2l6ZT01NiZ0eHQtY2xpcD1lbGxpcHNpcyZ0eHQtYWxpZ249bGVmdCUyQ3RvcCZzPTE4ZDNlMzY5YzY2MzY4Nzg4MWIyZGZlMzk3NmEzMTg1%26mark-x%3D142%26mark-y%3D112%26blend64%3DaHR0cHM6Ly9xaWl0YS11c2VyLWNvbnRlbnRzLmltZ2l4Lm5ldC9-dGV4dD9peGxpYj1yYi00LjAuMCZ3PTYxNiZ0eHQ9JTQwdHRhdHNmJnR4dC1jb2xvcj0lMjMyMTIxMjEmdHh0LWZvbnQ9SGlyYWdpbm8lMjBTYW5zJTIwVzYmdHh0LXNpemU9MzYmdHh0LWFsaWduPWxlZnQlMkN0b3Amcz1iZWYxZmZmYzcwM2ZkMjMyYjZiMDhlYmI3NjQzZGUxYw%26blend-x%3D142%26blend-y%3D491%26blend-mode%3Dnormal%26s%3D24c418faf6ea66d6c9ccb068838d1bb1)