downloadFile

1/**
2 * Triggers download of a file with specified content and name.
3 *
4 * @param content - The file content (as string or Blob).
5 * @param filename - The name of the file to be downloaded.
6 * @param mimeType - Optional MIME type (defaults to 'application/octet-stream').
7 */
8export function downloadFile(
9  content: string | Blob,
10  filename: string,
11  mimeType: string = 'application/octet-stream'
12): void {
13  const blob = content instanceof Blob ? content : new Blob([content], { type: mimeType });
14  const url = URL.createObjectURL(blob);
15
16  const a = document.createElement('a');
17  a.href = url;
18  a.download = filename;
19  a.style.display = 'none';
20
21  document.body.appendChild(a);
22  a.click();
23  document.body.removeChild(a);
24
25  URL.revokeObjectURL(url);
26}

1const originalCreateObjectURL = URL.createObjectURL;
2const originalRevokeObjectURL = URL.revokeObjectURL;
3
4beforeEach(() => {
5  URL.createObjectURL = jest.fn(() => 'blob:url');
6  URL.revokeObjectURL = jest.fn();
7  document.body.innerHTML = '';
8});
9
10afterEach(() => {
11  URL.createObjectURL = originalCreateObjectURL;
12  URL.revokeObjectURL = originalRevokeObjectURL;
13  jest.clearAllMocks();
14});
15
16test('creates a download link and clicks it', () => {
17  const clickSpy = jest.fn();
18  document.createElement = jest.fn(() => {
19    const a = document
20      .createElementNS('http://www.w3.org/1999/xhtml', 'a') as HTMLAnchorElement;
21    a.click = clickSpy;
22    return a;
23  }) as any;
24
25  downloadFile('Hello world', 'hello.txt', 'text/plain');
26
27  expect(URL.createObjectURL).toHaveBeenCalled();
28  expect(clickSpy).toHaveBeenCalled();
29  expect(URL.revokeObjectURL).toHaveBeenCalledWith('blob:url');
30});
31
32test('accepts Blob as input', () => {
33  const blob = new Blob(['data'], { type: 'text/plain' });
34  downloadFile(blob, 'file.txt');
35  expect(URL.createObjectURL).toHaveBeenCalledWith(blob);
36});