svelte-streamable/dist/index.js

Super tiny, simple to use SvelteJS store for real-time updates from server via SSE.

(function (global, factory) {
	typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports, require('svelte/store')) :
	typeof define === 'function' && define.amd ? define(['exports', 'svelte/store'], factory) :
	(global = typeof globalThis !== 'undefined' ? globalThis : global || self, factory(global.streamable = {}, global.store));
}(this, (function (exports, store) { 'use strict';

	const esx = {};

	function streamable(
		{ url, event = 'message', format = 'json', ...options },
		callback,
		defaultValue
	) {
		const auto = !callback || callback.length < 2;
		const initial = defaultValue ? Promise.resolve(defaultValue) : new Promise(noop);
		return store.readable(initial, (set) => {
			let cleanup = noop;

			function resolve(value) {
				set(typeof value !== 'undefined' ? Promise.resolve(value) : initial);
			}

			function update(e) {
				cleanup(false);

				let data;

				if (e && e.data) {
					if (format === 'json') {
						data = JSON.parse(e.data);
					} else if (format === 'base64') {
						data = atob(e.data);
					} else if (format === 'urlencoded') {
						data = Object.fromEntries(new URLSearchParams(e.data));
					} else {
						data = e.data;
					}
				}

				const result = callback ? callback(data, resolve) : data;

				if (auto) {
					resolve(result);
				} else {
					cleanup = typeof result === 'function' ? result : noop;
				}
			}

			function error(e) {
				set(Promise.reject(e));
			}

			const keypath = Object.entries(options)
				.sort()
				.reduce((k, [, v]) => `${k}/${v}`, url);

			let es = esx[keypath];

			if (!es) {
				es = new EventSource(url, options);
				es.subscribers = 0;
				esx[keypath] = es;
			}

			es.addEventListener('error', error);
			es.addEventListener(event, update);

			callback && setTimeout(update);

			es.subscribers++;

			return () => {
				es.removeEventListener('error', error);
				es.removeEventListener(event, update);

				if (!--es.subscribers) {
					es.close();
					delete esx[keypath];
				}

				cleanup(true);
			};
		});
	}

	function noop() {}

	exports.streamable = streamable;

	Object.defineProperty(exports, '__esModule', { value: true });

})));