Dealing with directories is not something you will cope with on a daily basis, but occasionally the use case arises, such as wanting to process all images in a directory. With the File System Access API, users can now open directories in the browser and decide if they need write access or not.
The modern way
Using the File System Access API's showDirectoryPicker() method
To open a directory, call
showDirectoryPicker(),
which returns a promise with the picked directory. If you need write access, you can pass { mode: 'readwrite' } to the method.
The classic way
Using the <input type="file" webkitdirectory> element
The <input type="file" webkitdirectory> element on a page allows the user to click it and open
a directory. The trick now consists of inserting the element invisibly into a page with JavaScript and click it programmatically.
Progressive enhancement
The method below uses the File System Access API when it's supported
and else falls back to the classic approach. In both cases the function
returns a directory, but in case of where the File System Access API
is supported, each file object also has a FileSystemDirectoryHandle stored in
the directoryHandle property and a FileSystemFileHandle stored in the handle property,
so you can optionally serialize the handles to disk.
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();
}
});
};
Further reading
Demo
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`));
});