Add before unmount tracking

Author: dolfbarr

src/index.test.tsx

@@ -74,6 +74,7 @@ describe('useLog', () => {
       logUnmount()
     })
     expect(consoleLog).toBeCalledWith('On unmount: null')
-    expect(consoleLog).toBeCalledTimes(6)
+    expect(consoleLog).toBeCalledWith('Before unmount: onChange 2s')
+    expect(consoleLog).toBeCalledTimes(7)
   })
 })

src/index.tsx

@@ -1,4 +1,4 @@
-import { useEffect } from 'react'
+import { useEffect, useRef } from 'react'
 
 export interface UseLogReturn {
   log: <T>(value: T) => void
@@ -7,6 +7,13 @@ export interface UseLogReturn {
 export const useLog = (): UseLogReturn => {
   function log<T>(value: T): void {
     return (() => {
+      const isUnmounting = useRef(false)
+      useEffect(() => {
+        return () => {
+          isUnmounting.current = true
+        }
+      }, [])
+
       useEffect(() => {
         console.log(`On mount: ${String(value)}`)
 
@@ -17,6 +24,12 @@ export const useLog = (): UseLogReturn => {
 
       useEffect(() => {
         console.log(`On change: ${String(value)}`)
+
+        return () => {
+          if (isUnmounting.current) {
+            console.log(`Before unmount: ${String(value)}`)
+          }
+        }
       }, [value])
     })()
   }