feat: immediate option, return start function

packages/core/usePerformanceObserver/index.ts

@@ -3,7 +3,14 @@ import { useSupported } from '../useSupported'
 import type { ConfigurableWindow } from '../_configurable'
 import { defaultWindow } from '../_configurable'
 
-export type UsePerformanceObserverOptions = PerformanceObserverInit & ConfigurableWindow
+export type UsePerformanceObserverOptions = PerformanceObserverInit & ConfigurableWindow & {
+  /**
+   * Start the observer immediate.
+   *
+   * @default true
+   */
+  immediate?: boolean
+}
 
 /**
  * Observe performance metrics.
@@ -14,22 +21,34 @@ export type UsePerformanceObserverOptions = PerformanceObserverInit & Configurab
 export function usePerformanceObserver(options: UsePerformanceObserverOptions, callback: PerformanceObserverCallback) {
   const {
     window = defaultWindow,
+    immediate = true,
     ...performanceOptions
   } = options
 
   const isSupported = useSupported(() => window && 'PerformanceObserver' in window)
 
-  const observer = new PerformanceObserver(callback)
-  observer.observe(performanceOptions)
+  let observer: PerformanceObserver | undefined
 
   const stop = () => {
     observer?.disconnect()
   }
 
+  const start = () => {
+    if (isSupported.value) {
+      stop()
+      observer = new PerformanceObserver(callback)
+      observer.observe(performanceOptions)
+    }
+  }
+
   tryOnScopeDispose(stop)
 
+  if (immediate)
+    start()
+
   return {
     isSupported,
+    start,
     stop,
   }
 }