Fix babel build error, convert Poll class into a function

src/utils/poll.ts

@@ -1,93 +1,89 @@
 const DEFAULT_INTERVAL = 15000;
 const DEFAULT_GRACE_RATIO = 0.33;
 
-export class Poll {
-	private _cancelled = true;
-
-	// This flag is true when the poll is not running. You may
-	// use it in your code to determine if you should proceed.
-	public get cancelled(): boolean {
-		return this._cancelled;
-	}
-
-	private _counter = 0;
-	public get counter(): number {
-		return this._counter;
-	}
-
-	private graceInterval: number;
-	private pollInterval: NodeJS.Timer | null = null;
-	private lastCompleteTime = 0;
-	private blocked = false;
-	private isTabActive: boolean;
+export interface Poll {
+	poll: (opts?: { forced?: boolean }) => void;
+	start: () => void;
+	stop: () => void;
+	destroy: () => void;
+}
 
-	constructor(
-		private fn: (poll: Poll) => Promise<any>,
-		private interval: number,
-		graceRatio: number,
-		isTabActive: boolean,
-	) {
-		this.poll = this.poll.bind(this);
-		this.graceInterval = this.interval * graceRatio;
-		this.isTabActive = isTabActive;
-	}
+const pollFactory = (
+	fn: () => Promise<any>,
+	interval: number,
+	graceRatio: number,
+	isTabActive: boolean,
+) => {
+	let cancelled = true;
+	const graceInterval: number = interval * graceRatio;
+	let pollInterval: NodeJS.Timer | null = null;
+	let lastCompleteTime = 0;
+	let counter = 0;
+	let blocked = false;
 
-	public async poll(opts?: { forced?: boolean }) {
+	const poll = async (opts?: { forced?: boolean }) => {
 		// Only run poll if the previous call has finished and the poll
 		// is not cancelled
-		if (this.cancelled || this.blocked) {
+		if (cancelled || blocked) {
 			return;
 		}
 
 		const forced = opts && opts.forced;
 		// Return if we're invisible, unless it's first run
-		if (!forced && !this.isTabActive && this.lastCompleteTime !== 0) {
+		if (!forced && !isTabActive && lastCompleteTime !== 0) {
 			return;
 		}
-		if (!forced && Date.now() - this.lastCompleteTime < this.graceInterval) {
+		if (!forced && Date.now() - lastCompleteTime < graceInterval) {
 			return;
 		}
-		this.blocked = true;
+		blocked = true;
 
 		try {
-			await this.fn(this);
-			this.lastCompleteTime = Date.now();
+			await fn();
+			lastCompleteTime = Date.now();
 		} finally {
-			this._counter++;
-			this.blocked = false;
+			counter++;
+			blocked = false;
 		}
-	}
+	};
 
-	public start() {
+	const start = () => {
 		// Only start polling if it is currently stopped.
-		if (this.pollInterval != null) {
+		if (pollInterval != null) {
 			return;
 		}
-		this.lastCompleteTime = 0;
-		this._cancelled = false;
-		this.pollInterval = setInterval(this.poll, this.interval);
+		lastCompleteTime = 0;
+		cancelled = false;
+		pollInterval = setInterval(poll, interval);
 		// Also run a poll instantly, as we wanted to start it *now*,
 		// not X time in the future.
-		return this.poll();
-	}
+		return poll();
+	};
 
-	public stop() {
-		if (this.pollInterval) {
-			clearInterval(this.pollInterval);
+	const stop = () => {
+		if (pollInterval) {
+			clearInterval(pollInterval);
 		}
-		this._cancelled = true;
-		this.pollInterval = null;
-	}
+		cancelled = true;
+		pollInterval = null;
+	};
 
-	public destroy() {
-		this.stop();
-		this.fn = async () => undefined; // break possible cyclic reference
-	}
-}
+	const destroy = () => {
+		stop();
+		fn = async () => undefined; // break possible cyclic reference
+	};
+
+	return {
+		poll,
+		start,
+		stop,
+		destroy,
+	};
+};
 
 export const createPoll = (
-	fn: (poll: Poll) => Promise<any>,
+	fn: () => Promise<any>,
 	interval: number = DEFAULT_INTERVAL,
 	isTabActive: boolean = true,
 	graceRatio: number = DEFAULT_GRACE_RATIO,
-) => new Poll(fn, interval, graceRatio, isTabActive);
+) => pollFactory(fn, interval, graceRatio, isTabActive);