1. <head>
    2.     <meta charset="UTF-8">
    3.     <meta name="viewport" content="width=device-width, initial-scale=1.0">
    4.     <title>Document</title>
    5. </head>
    6. <body>
    7.     <div id="app">
    8.         app
    9.         <div class="one">one1</div>
    10.         <div class="one">one1</div>
    11.         <div class="one">one1</div>
    12.     </div>
    13.     <script>
    14.         var app = document.getElementById("app");
    15.         console.log(app);
    16.         // NodeList
    17.         var all = document.querySelectorAll(".one");
    18.         console.log(all)
    20.     </script>
    21. </body>
    22. </html>

    1.PNG