querySelectorAll でノードを取得したら Array でなく NodeList なので map メソッドがない。 調べたら call メソッドを使うことで解決できた。 <!DOCTYPE html> <html> <head> <meta charset="utf-8" /> <title>call sample</title> <script type="text/javascript"> addEventListener('DOMContentLoaded', function () { var elms = document.querySelectorAll('tr>td:nth-child(2)'); var names = Array.prototype.map.call(elms, function (elm) { return elm.firstChild.da
![NodeList に map メソッドがない(call の使い方) - Qiita](https://cdn-ak-scissors.b.st-hatena.com/image/square/c77cbe51d47f381ebb19983fa81706daefe65270/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-dGV4dD9peGxpYj1yYi00LjAuMCZ3PTkxNiZoPTMzNiZ0eHQ9Tm9kZUxpc3QlMjAlRTMlODElQUIlMjBtYXAlMjAlRTMlODMlQTElRTMlODIlQkQlRTMlODMlODMlRTMlODMlODklRTMlODElOEMlRTMlODElQUElRTMlODElODQlMjhjYWxsJTIwJUUzJTgxJUFFJUU0JUJEJUJGJUUzJTgxJTg0JUU2JTk2JUI5JTI5JnR4dC1jb2xvcj0lMjMyMTIxMjEmdHh0LWZvbnQ9SGlyYWdpbm8lMjBTYW5zJTIwVzYmdHh0LXNpemU9NTYmdHh0LWNsaXA9ZWxsaXBzaXMmdHh0LWFsaWduPWxlZnQlMkN0b3Amcz1hMTAyMzQ2ZTNmNTQxYzg0ODU0YTg5NzVkZWM2MTg0NQ%26mark-x%3D142%26mark-y%3D112%26blend64%3DaHR0cHM6Ly9xaWl0YS11c2VyLWNvbnRlbnRzLmltZ2l4Lm5ldC9-dGV4dD9peGxpYj1yYi00LjAuMCZ3PTYxNiZ0eHQ9JTQwbWFyY2llMDAxJnR4dC1jb2xvcj0lMjMyMTIxMjEmdHh0LWZvbnQ9SGlyYWdpbm8lMjBTYW5zJTIwVzYmdHh0LXNpemU9MzYmdHh0LWFsaWduPWxlZnQlMkN0b3Amcz05YWU1YzRiMDYwNWE5NDU2MDNiYTUwYTNiYjVjZTM5Mw%26blend-x%3D142%26blend-y%3D491%26blend-mode%3Dnormal%26s%3Dfc2c9d8fb00f4a6c453204bfd93e87fa)