並列で実行したい場合は Promise.all([promise...]) すれば事足りるんだけど、直列で実行しようとするとちょっとややこしい。 # 実行すると1秒後に実行回数をprintするPromise化された関数 cnt = 0 f = -> new Promise (done) -> setTimeout (-> console.log 'done', cnt++ done() ), 1000 # fを直列に4回実行する promises = [f, f, f, f] seq = promises.reduce ((ret, p) -> ret.then p ), promises.shift()() seq.then => console.log 'finish'
![Promiseを直列で実行する - Qiita](https://cdn-ak-scissors.b.st-hatena.com/image/square/1bfccf3c800b3c86c03f1aee44091544624835af/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-dGV4dD9peGxpYj1yYi00LjAuMCZ3PTkxNiZoPTMzNiZ0eHQ9UHJvbWlzZSVFMyU4MiU5MiVFNyU5QiVCNCVFNSU4OCU5NyVFMyU4MSVBNyVFNSVBRSU5RiVFOCVBMSU4QyVFMyU4MSU5OSVFMyU4MiU4QiZ0eHQtY29sb3I9JTIzMjEyMTIxJnR4dC1mb250PUhpcmFnaW5vJTIwU2FucyUyMFc2JnR4dC1zaXplPTU2JnR4dC1jbGlwPWVsbGlwc2lzJnR4dC1hbGlnbj1sZWZ0JTJDdG9wJnM9ZjRkMWFkNTg2YjIxMzQyNzE5NTU4NmJiMGZhMzRiZDY%26mark-x%3D142%26mark-y%3D112%26blend64%3DaHR0cHM6Ly9xaWl0YS11c2VyLWNvbnRlbnRzLmltZ2l4Lm5ldC9-dGV4dD9peGxpYj1yYi00LjAuMCZ3PTYxNiZ0eHQ9JTQwbWl6Y2hpJnR4dC1jb2xvcj0lMjMyMTIxMjEmdHh0LWZvbnQ9SGlyYWdpbm8lMjBTYW5zJTIwVzYmdHh0LXNpemU9MzYmdHh0LWFsaWduPWxlZnQlMkN0b3Amcz04YTUwN2I0MDFmMDRhMzM1YzQ4NmVjMWRkMjZjZWJmOQ%26blend-x%3D142%26blend-y%3D491%26blend-mode%3Dnormal%26s%3D1bc6ab03c936d33071fe279fd7ff98a6)