如何開啟目錄

Thomas Steiner

您不常需要處理目錄，但偶爾會遇到這類情況，例如想要處理目錄中的所有圖片。現在使用者可以透過 File System Access API 在瀏覽器中開啟目錄，並決定是否需要寫入權限。

現代做法

使用 File System Access API 的 showDirectoryPicker() 方法

如要開啟目錄，請呼叫 showDirectoryPicker()，這會傳回包含所選目錄的 Promise。如需寫入權限，您可以將 { mode: 'readwrite' } 傳遞至方法。

Browser Support

  • Chrome: 86.
  • Edge: 86.
  • Firefox: not supported.
  • Safari: not supported.

Source

傳統做法

使用 <input type="file" webkitdirectory> 元素

網頁上的 <input type="file" webkitdirectory> 元素可供使用者點選並開啟目錄。現在的訣竅是使用 JavaScript 將元素隱形插入網頁，然後以程式輔助方式點選該元素。

Browser Support

  • Chrome: 7.
  • Edge: 13.
  • Firefox: 50.
  • Safari: 11.1.

Source

漸進增強

如果支援 File System Access API，下列方法就會使用該 API，否則會改用傳統做法。在這兩種情況下，函式都會傳回目錄，但如果支援 File System Access API，每個檔案物件也會在 directoryHandle 屬性中儲存 FileSystemDirectoryHandle，並在 handle 屬性中儲存 FileSystemFileHandle，因此您可以選擇將控制代碼序列化至磁碟。

const openDirectory = async (mode = "read") => {
  // Feature detection. The API needs to be supported
  // and the app not run in an iframe.
  const supportsFileSystemAccess =
    "showDirectoryPicker" in window &&
    (() => {
      try {
        return window.self === window.top;
      } catch {
        return false;
      }
    })();
  // If the File System Access API is supported…
  if (supportsFileSystemAccess) {
    let directoryStructure = undefined;

    // Recursive function that walks the directory structure.
    const getFiles = async (dirHandle, path = dirHandle.name) => {
      const dirs = [];
      const files = [];
      for await (const entry of dirHandle.values()) {
        const nestedPath = `${path}/${entry.name}`;
        if (entry.kind === "file") {
          files.push(
            entry.getFile().then((file) => {
              file.directoryHandle = dirHandle;
              file.handle = entry;
              return Object.defineProperty(file, "webkitRelativePath", {
                configurable: true,
                enumerable: true,
                get: () => nestedPath,
              });
            })
          );
        } else if (entry.kind === "directory") {
          dirs.push(getFiles(entry, nestedPath));
        }
      }
      return [
        ...(await Promise.all(dirs)).flat(),
        ...(await Promise.all(files)),
      ];
    };

    try {
      // Open the directory.
      const handle = await showDirectoryPicker({
        mode,
      });
      // Get the directory structure.
      directoryStructure = getFiles(handle, undefined);
    } catch (err) {
      if (err.name !== "AbortError") {
        console.error(err.name, err.message);
      }
    }
    return directoryStructure;
  }
  // Fallback if the File System Access API is not supported.
  return new Promise((resolve) => {
    const input = document.createElement('input');
    input.type = 'file';
    input.webkitdirectory = true;

    input.addEventListener('change', () => {
      let files = Array.from(input.files);
      resolve(files);
    });
    if ('showPicker' in HTMLInputElement.prototype) {
      input.showPicker();
    } else {
      input.click();
    }
  });
};

延伸閱讀

示範

HTML

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="utf-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1" />
    <link
      rel="icon"
      href="data:image/svg+xml,<svg xmlns=%22http://www.w3.org/2000/svg%22 viewBox=%220 0 100 100%22><text y=%22.9em%22 font-size=%2290%22>📂</text></svg>"
    />
    <title>How to open a directory</title>
  </head>
  <body>
    <h1>How to open a directory</h1>
    <button type="button">Open directory</button>
    <pre></pre>
  </body>
</html>

CSS


        :root {
  color-scheme: dark light;
}

html {
  box-sizing: border-box;
}

*,
*:before,
*:after {
  box-sizing: inherit;
}

body {
  margin: 1rem;
  font-family: system-ui, sans-serif;
}

JS


        const button = document.querySelector('button');
const pre = document.querySelector('pre');

const openDirectory = async (mode = "read") => {
  // Feature detection. The API needs to be supported
  // and the app not run in an iframe.
  const supportsFileSystemAccess =
    "showDirectoryPicker" in window &&
    (() => {
      try {
        return window.self === window.top;
      } catch {
        return false;
      }
    })();
  // If the File System Access API is supported…
  if (supportsFileSystemAccess) {
    let directoryStructure = undefined;

    const getFiles = async (dirHandle, path = dirHandle.name) => {
      const dirs = [];
      const files = [];
      for await (const entry of dirHandle.values()) {
        const nestedPath = `${path}/${entry.name}`;
        if (entry.kind === "file") {
          files.push(
            entry.getFile().then((file) => {
              file.directoryHandle = dirHandle;
              file.handle = entry;
              return Object.defineProperty(file, "webkitRelativePath", {
                configurable: true,
                enumerable: true,
                get: () => nestedPath,
              });
            })
          );
        } else if (entry.kind === "directory") {
          dirs.push(getFiles(entry, nestedPath));
        }
      }
      return [
        ...(await Promise.all(dirs)).flat(),
        ...(await Promise.all(files)),
      ];
    };

    try {
      const handle = await showDirectoryPicker({
        mode,
      });
      directoryStructure = getFiles(handle, undefined);
    } catch (err) {
      if (err.name !== "AbortError") {
        console.error(err.name, err.message);
      }
    }
    return directoryStructure;
  }
  // Fallback if the File System Access API is not supported.
  return new Promise((resolve) => {
    const input = document.createElement('input');
    input.type = 'file';
    input.webkitdirectory = true;

    input.addEventListener('change', () => {
      let files = Array.from(input.files);
      resolve(files);
    });
    if ('showPicker' in HTMLInputElement.prototype) {
      input.showPicker();
    } else {
      input.click();
    }
  });
};

button.addEventListener('click', async () => {
  const filesInDirectory = await openDirectory();
  if (!filesInDirectory) {
    return;
  }
  Array.from(filesInDirectory).forEach((file) => (pre.textContent += `${file.name}\n`));
});