Fix page switching breaking chart

manifest.json

@@ -1,7 +1,7 @@
 {
   "name": "TimeChimp Billability Chart",
   "description": "Adds a billability chart on the TimeChimp hours page.",
-  "version": "1.3.0",
+  "version": "1.3.1",
   "manifest_version": 3,
   "permissions": [
     "webRequest"

src/content/add-billability-chart.ts

@@ -30,15 +30,16 @@ async function doAddBillabilityChart(date: Date, userId: number) {
         return;
     }
 
-    let chartContainer = addTimePanel.querySelector('#billability-card');
-    if (!chartContainer) {
+    // Check if the chart container already exists.
+    // If not, create a new element which can be used as the chart parent.
+    let chartContainer: HTMLElement | undefined;
+    if (!addTimePanel.querySelector('#billability-card')) {
         chartContainer = addTimePanel.appendChild(createBillabilityCard());
     }
 
     const times = await getTimes(userId, date, GET_TIMES_WEEKS);
-
     const stats = calculateTimeStats(times, SHOW_WEEKS, ROLLING_AVG_WEEKS);
-    createOrUpdateChart(chartContainer as HTMLElement, stats);
+    createOrUpdateChart(stats, chartContainer);
 }
 
 function createBillabilityCard() {

src/content/chart.ts

@@ -10,11 +10,11 @@ const textStyle = {
     fontSize: '12px',
 };
 
-let chart: Highcharts.Chart;
+let chart: Highcharts.Chart | undefined;
 
 export function createOrUpdateChart(
-    element: HTMLElement,
     rollingStats: RollingStats[],
+    element?: HTMLElement,
 ) {
     const options: Highcharts.Options = {
         chart: {
@@ -115,11 +115,13 @@ export function createOrUpdateChart(
         },
     };
 
-    if (chart) {
-        console.debug('Updating existing chart');
+    if (element) {
+        console.debug('Creating new chart.');
+        chart = Highcharts.chart(element, options);
+    } else if (chart) {
+        console.debug('Updating existing chart.');
         chart.update(options);
     } else {
-        console.debug('Creating new chart');
-        chart = Highcharts.chart(element, options);
+        console.error('No chart container given and no existing chart set.');
     }
 }