HTML 拖曳介面可讓網頁應用程式接受拖曳和捨棄的檔案。在拖曳作業期間，拖曳的檔案和目錄項目會分別與檔案項目和目錄項目建立關聯。如要將檔案拖曳至瀏覽器，有兩種方法可供選擇：新式與傳統。
新穎時尚
使用 File System Access API 的 DataTransferItem.getAsFileSystemHandle() 方法
如果拖曳的項目是檔案，DataTransferItem.getAsFileSystemHandle() 方法會傳回具有 FileSystemFileHandle 物件的 Commit，如果拖曳項目為目錄，則會傳回 FileSystemDirectoryHandle 物件的保證。這些控點可讓您讀取檔案或目錄，並視需要寫入。請注意，「拖曳」介面的 DataTransferItem.kind 會是檔案「和」目錄的 "file"，而 File System Access API 的 FileSystemHandle.kind 則是 "file" 的檔案，而目錄則為 "directory"。
經典風格
使用非標準 DataTransferItem.webkitGetAsEntry() 方法
如果項目是檔案，DataTransferItem.webkitGetAsEntry() 方法會傳回拖曳資料項目的 FileSystemFileEntry，如果項目是目錄，則傳回 FileSystemDirectoryEntry。您雖然可以讀取檔案或目錄，但無法寫回這些內容。這種方法的缺點是不符合標準測試群組，但具有支援目錄的優勢。
漸進增強
下列程式碼片段在支援的情況下使用新型 File System Access API 的 DataTransferItem.getAsFileSystemHandle() 方法，接著改回非標準 DataTransferItem.webkitGetAsEntry() 方法，最後改回使用傳統 DataTransferItem.getAsFile() 方法。請務必檢查每個 handle 的類型，因為其類型可能為：
- 選擇新式程式碼路徑時，
FileSystemDirectoryHandle。 - 選擇非標準程式碼路徑時，
FileSystemDirectoryEntry。
所有類型都有 name 屬性，因此記錄功能正確無誤，能隨時正常運作。
// Run feature detection.
const supportsFileSystemAccessAPI =
'getAsFileSystemHandle' in DataTransferItem.prototype;
const supportsWebkitGetAsEntry =
'webkitGetAsEntry' in DataTransferItem.prototype;
// This is the drag and drop zone.
const elem = document.querySelector('main');
// Prevent navigation.
elem.addEventListener('dragover', (e) => {
e.preventDefault();
});
// Visually highlight the drop zone.
elem.addEventListener('dragenter', (e) => {
elem.style.outline = 'solid red 1px';
});
// Visually unhighlight the drop zone.
elem.addEventListener('dragleave', (e) => {
elem.style.outline = '';
});
// This is where the drop is handled.
elem.addEventListener('drop', async (e) => {
// Prevent navigation.
e.preventDefault();
if (!supportsFileSystemAccessAPI && !supportsWebkitGetAsEntry) {
// Cannot handle directories.
return;
}
// Unhighlight the drop zone.
elem.style.outline = '';
// Prepare an array of promises…
const fileHandlesPromises = [...e.dataTransfer.items]
// …by including only files (where file misleadingly means actual file _or_
// directory)…
.filter((item) => item.kind === 'file')
// …and, depending on previous feature detection…
.map((item) =>
supportsFileSystemAccessAPI
// …either get a modern `FileSystemHandle`…
? item.getAsFileSystemHandle()
// …or a classic `FileSystemFileEntry`.
: item.webkitGetAsEntry(),
);
// Loop over the array of promises.
for await (const handle of fileHandlesPromises) {
// This is where we can actually exclusively act on the directories.
if (handle.kind === 'directory' || handle.isDirectory) {
console.log(`Directory: ${handle.name}`);
}
}
});
其他資訊
示範
HTML
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1" />
<title>How to drag and drop directories</title>
</head>
<body>
<main>
<h1>How to drag and drop directories</h1>
<p>Drag and drop one or multiple files or directories onto the page.</p>
<pre></pre>
</main>
</body>
</html>CSS
:root {
color-scheme: dark light;
box-sizing: border-box;
}
*,
*:before,
*:after {
box-sizing: inherit;
}
body {
margin: 0;
padding: 1rem;
font-family: system-ui, sans-serif;
line-height: 1.5;
min-height: 100vh;
display: flex;
flex-direction: column;
}
img,
video {
height: auto;
max-width: 100%;
}
main {
flex-grow: 1;
}
footer {
margin-top: 1rem;
border-top: solid CanvasText 1px;
font-size: 0.8rem;
}
JS
const supportsFileSystemAccessAPI =
"getAsFileSystemHandle" in DataTransferItem.prototype;
const supportsWebkitGetAsEntry =
"webkitGetAsEntry" in DataTransferItem.prototype;
const elem = document.querySelector("main");
const debug = document.querySelector("pre");
elem.addEventListener("dragover", (e) => {
// Prevent navigation.
e.preventDefault();
});
elem.addEventListener("dragenter", (e) => {
elem.style.outline = "solid red 1px";
});
elem.addEventListener("dragleave", (e) => {
elem.style.outline = "";
});
elem.addEventListener("drop", async (e) => {
e.preventDefault();
elem.style.outline = "";
const fileHandlesPromises = [...e.dataTransfer.items]
.filter((item) => item.kind === "file")
.map((item) =>
supportsFileSystemAccessAPI
? item.getAsFileSystemHandle()
: supportsWebkitGetAsEntry
? item.webkitGetAsEntry()
: item.getAsFile()
);
for await (const handle of fileHandlesPromises) {
if (handle.kind === "directory" || handle.isDirectory) {
console.log(`Directory: ${handle.name}`);
debug.textContent += `Directory: ${handle.name}\n`;
} else {
console.log(`File: ${handle.name}`);
debug.textContent += `File: ${handle.name}\n`;
}
}
});