1 files changed, 29 insertions, 0 deletions
diff --git a/src/AppProfiler.tsx b/src/AppProfiler.tsx
new file mode 100644
index 000000000..31a4cc54e
--- /dev/null
+++ b/src/AppProfiler.tsx
@@ -0,0 +1,29 @@
+import React, {Profiler} from 'react'
+
+// Don't let it get stripped out in profiling builds (which apply production Babel preset).
+const log = (global as any)['con' + 'sole'].log
+
+function onRender(id: string, phase: string, actualDuration: number) {
+  if (!__DEV__) {
+    // This block of code will exist in the production build of the app.
+    // However, only profiling builds of React call `onRender` so it's dead code in actual production.
+    const message = `<Profiler> ${id}:${phase} ${
+      actualDuration > 500
+        ? '(╯°□°）╯ '
+        : actualDuration > 100
+        ? '[!!] '
+        : actualDuration > 16
+        ? '[!] '
+        : ''
+    }${Math.round(actualDuration)}ms`
+    log(message)
+  }
+}
+
+export function AppProfiler({children}: {children: React.ReactNode}) {
+  return (
+    <Profiler id="app" onRender={onRender}>
+      {children}
+    </Profiler>
+  )
+}