回答

可以使用file system access api来通过js在浏览器中对本地文件或文件夹进行读取修改，

老版本的Window.chooseFileSystemEntries() 已经弃用了，改成新版本的三个方法

 Window.showOpenFilePicker(), Window.showSaveFilePicker(), 和Window.showDirectoryPicker()

下面我们代码演示一下通过js在浏览器中读写本地的文件，代码如下：

<html>

<head>
    <script src="//repo.bfw.wiki/bfwrepo/js/eruda.js"></script>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width,initial-scale=1.0,maximum=1.0,minimum=1.0,user-scalable=0" />
    <title>BFW NEW PAGE</title>
    <link type="text/css" rel="stylesheet" href="//repo.bfw.wiki/bfwrepo/css/bootstrap.4.3.1.min.css">
    <style>
        body{
            padding: 10px;
        }
    </style>
</head>

<body>
    <p><button id="openlocalfile">打开本地文件</button>

        <button id="savetolocalfile">保存到本地</button>不要在iframe中打开</p>

    <textarea id="editor" style="width:100%;height:400px;"></textarea>
    <script>
        const openbtn = document.getElementById('openlocalfile');
          const editor = document.getElementById('editor');
      const savebtn = document.getElementById('savetolocalfile');
      let fileHandle;
            
        openbtn.addEventListener('click', async () => {
      [fileHandle] = await window.showOpenFilePicker();
      const file = await fileHandle.getFile();
      const contents = await file.text();
      editor.value = contents;
    });
    
     savebtn.addEventListener('click', async () => {
         if(fileHandle==null){
               alert("请先打开一个本地文件后进行修改");
               return;
         }
           const writable = await fileHandle.createWritable();
          // Write the contents of the file to the stream.
          await writable.write(editor.value);
          // Close the file and write the contents to disk.
          await writable.close();
        alert("修改本地文件成功");
    });
    </script>
</body>

</html>