How to open a directory
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.
- Chrome 86, Supported 86
- Firefox, Not supported
- Edge 86, Supported 86
- Safari, Not supported
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.
- Chrome 7, Supported 7
- Firefox 50, Supported 50
- Edge 13, Supported 13
- Safari 11.1, Supported 11.1
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 #
<!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>đź“‚</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>
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`));
});
:root {
color-scheme: dark light;
}
html {
box-sizing: border-box;
}
*,
*:before,
*:after {
box-sizing: inherit;
}
body {
margin: 1rem;
font-family: system-ui, sans-serif;
}