Refactor timers into a simple tested object.

src/utils/timer.ts

@@ -0,0 +1,29 @@
+export class Timer {
+  protected _timer: number | null = null;
+
+  public stop(): void {
+    if (this._timer) {
+      window.clearTimeout(this._timer);
+      this._timer = null;
+    }
+  }
+
+  public isRunning(): boolean {
+    return this._timer !== null;
+  }
+
+  public start(seconds: number, func: () => void): void {
+    this.stop();
+    this._timer = window.setTimeout(() => {
+      this._timer = null;
+      func();
+    }, seconds * 1000);
+  }
+
+  public startRepeated(seconds: number, func: () => void): void {
+    this.stop();
+    this._timer = window.setInterval(() => {
+      func();
+    }, seconds * 1000);
+  }
+}