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SvelteKit SSE
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| import { sse } from '$lib'; | |
| import type { RequestHandler } from './$types'; | |
| export const GET: RequestHandler = async () => { | |
| return sse<number>(async ({ write, onClose }) => { | |
| const id = setInterval(() => { | |
| write({ data: Date.now() }); | |
| }, 1000); | |
| onClose(() => { | |
| clearInterval(id); | |
| }); | |
| }); | |
| }; |
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| type Chunk<T> = { event?: string; id?: string | number; data: T }; | |
| export interface SSEResponseOptions extends ResponseInit { | |
| retry?: number; | |
| } | |
| export interface SSE<T> { | |
| write(chunk: Chunk<T>): Promise<boolean>; | |
| close(): Promise<void>; | |
| onClose(cb: () => void | Promise<void>): void; | |
| } | |
| export function sse<T>( | |
| run: (sse: SSE<T>) => Promise<void> | (() => void), | |
| options: SSEResponseOptions = {}, | |
| ) { | |
| return new SSEResponse(run, options); | |
| } | |
| export class SSEResponse<T> extends Response { | |
| constructor( | |
| run: (sse: SSE<T>) => Promise<void> | (() => void), | |
| { retry, headers, status, statusText }: SSEResponseOptions = {}, | |
| ) { | |
| let open = true; | |
| const { readable, writable } = new TransformStream<Chunk<T>, string>({ | |
| start: (controller) => { | |
| if (retry && retry > 0) controller.enqueue(`retry: ${retry}\n\n`); | |
| }, | |
| transform: ({ event, id, data }, controller) => { | |
| let msg = ''; | |
| // id | |
| if (id) msg += `id: ${id}\n`; | |
| // event | |
| if (event) msg += `event: ${event}\n`; | |
| // data | |
| if (typeof data === 'string') { | |
| msg += 'data: ' + data.trim().replace(/\n+/gm, '\ndata: ') + '\n'; | |
| } else { | |
| msg += `data: ${JSON.stringify(data)}\n`; | |
| } | |
| controller.enqueue(msg + '\n'); | |
| }, | |
| }); | |
| const writer = writable.getWriter(); | |
| const closePromise = writer.closed | |
| .then(() => { | |
| typeof cleanup === 'function' && cleanup(); | |
| }) | |
| .catch(() => { | |
| /* request aborted, do nothing */ | |
| }) | |
| .finally(() => { | |
| open = false; | |
| }); | |
| const cleanup = run({ | |
| async write(chunk) { | |
| if (!open) return false; | |
| await writer.write(chunk); | |
| return true; | |
| }, | |
| async close() { | |
| if (!open) return; | |
| writer.releaseLock(); | |
| await writable.close(); | |
| }, | |
| onClose(cb) { | |
| closePromise.then(() => { | |
| cb(); | |
| }); | |
| }, | |
| }); | |
| headers = new Headers(headers); | |
| if (!headers.has('Cache-Control')) { | |
| headers.set('Cache-Control', 'no-cache'); | |
| } | |
| headers.set('Content-Type', 'text/event-stream'); | |
| super(readable, { | |
| headers, | |
| status, | |
| statusText, | |
| }); | |
| } | |
| } |
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