feat(js): Improve tracesSampler example (#10591)

This was partially done here: #10544 but one place was forgotten.

Author: mydea

platform-includes/performance/traces-sampler-as-sampler/javascript.mdx

@@ -1,25 +1,41 @@
-```javascript
+```typescript
+// The shape of samplingContext that is passed to the tracesSampler function
+interface SamplingContext {
+  // Name of the span
+  name: string;
+  // Initial attributes of the span
+  attributes: SpanAttributes | undefined;
+  // If the parent span was sampled - undefined if there is no parent span
+  parentSampled: boolean | undefined;
+}
+
 Sentry.init({
   // ...
 
-  tracesSampler: samplingContext => {
-    // Examine provided context data (including parent decision, if any) along
-    // with anything in the global namespace to compute the sample rate or
-    // sampling decision for this transaction
+  tracesSampler: ({ name, attributes, parentSampled }) => {
+    // Do not sample health checks ever
+    if (name.includes("healthcheck")) {
+      // Drop this completelty, by setting its sample rate to 0%
+      return 0;
+    }
 
-    if ("...") {
-      // These are important - take a big sample
+    // These are important - take a big sample
+    if (name.includes("auth")) {
       return 1;
-    } else if ("...") {
-      // These are less important or happen much more frequently - only take 1%
+    }
+
+    // These are less important or happen much more frequently - only take 1%
+    if (name.includes("comment")) {
       return 0.01;
-    } else if ("...") {
-      // These aren't something worth tracking - drop all transactions like this
-      return 0;
-    } else {
-      // Default sample rate
-      return 0.5;
     }
-  };
+
+    // Continue trace decision, if there is any parentSampled information
+    if (typeof parentSampled === "boolean") {
+      return parentSampled;
+    }
+
+    // Else, use default sample rate
+    return 0.5;
+  },
 });
 ```