From 3f07b047df4d66f83047a5bb747c0a1665bceb6c Mon Sep 17 00:00:00 2001
From: crupest <crupest@outlook.com>
Date: Sun, 1 May 2022 21:30:31 +0800
Subject: ...

---
 FrontEnd/src/utilities/hooks.ts                    | 10 +----
 .../hooks/useReverseScrollPositionRemember.ts      |  2 +
 FrontEnd/src/utilities/hooks/useScrollToBottom.ts  | 45 ++++++++++++++++++++++
 FrontEnd/src/utilities/hooks/useScrollToTop.ts     | 43 ---------------------
 4 files changed, 49 insertions(+), 51 deletions(-)
 create mode 100644 FrontEnd/src/utilities/hooks/useScrollToBottom.ts
 delete mode 100644 FrontEnd/src/utilities/hooks/useScrollToTop.ts

(limited to 'FrontEnd/src/utilities')

diff --git a/FrontEnd/src/utilities/hooks.ts b/FrontEnd/src/utilities/hooks.ts
index c499b36b..a59f7167 100644
--- a/FrontEnd/src/utilities/hooks.ts
+++ b/FrontEnd/src/utilities/hooks.ts
@@ -1,11 +1,5 @@
 import useClickOutside from "./hooks/useClickOutside";
-import useReverseScrollPositionRemember from "./hooks/useReverseScrollPositionRemember";
-import useScrollToTop from "./hooks/useScrollToTop";
+import useScrollToBottom from "./hooks/useScrollToBottom";
 import { useIsSmallScreen } from "./hooks/mediaQuery";
 
-export {
-  useClickOutside,
-  useReverseScrollPositionRemember,
-  useScrollToTop,
-  useIsSmallScreen,
-};
+export { useClickOutside, useScrollToBottom, useIsSmallScreen };
diff --git a/FrontEnd/src/utilities/hooks/useReverseScrollPositionRemember.ts b/FrontEnd/src/utilities/hooks/useReverseScrollPositionRemember.ts
index 6fdd4b43..c0b6ce2c 100644
--- a/FrontEnd/src/utilities/hooks/useReverseScrollPositionRemember.ts
+++ b/FrontEnd/src/utilities/hooks/useReverseScrollPositionRemember.ts
@@ -1,3 +1,5 @@
+// Not used now!!! But preserved for future use.
+
 import React from "react";
 
 let on = false;
diff --git a/FrontEnd/src/utilities/hooks/useScrollToBottom.ts b/FrontEnd/src/utilities/hooks/useScrollToBottom.ts
new file mode 100644
index 00000000..f6780d9f
--- /dev/null
+++ b/FrontEnd/src/utilities/hooks/useScrollToBottom.ts
@@ -0,0 +1,45 @@
+import React from "react";
+import { fromEvent } from "rxjs";
+import { filter, throttleTime } from "rxjs/operators";
+
+function useScrollToBottom(
+  handler: () => void,
+  enable = true,
+  option = {
+    maxOffset: 5,
+    throttle: 1000,
+  }
+): void {
+  const handlerRef = React.useRef<(() => void) | null>(null);
+
+  React.useEffect(() => {
+    handlerRef.current = handler;
+
+    return () => {
+      handlerRef.current = null;
+    };
+  }, [handler]);
+
+  React.useEffect(() => {
+    const subscription = fromEvent(window, "scroll")
+      .pipe(
+        filter(
+          () =>
+            window.scrollY >=
+            document.body.scrollHeight - window.innerHeight - option.maxOffset
+        ),
+        throttleTime(option.throttle)
+      )
+      .subscribe(() => {
+        if (enable) {
+          handlerRef.current?.();
+        }
+      });
+
+    return () => {
+      subscription.unsubscribe();
+    };
+  }, [enable, option.maxOffset, option.throttle]);
+}
+
+export default useScrollToBottom;
diff --git a/FrontEnd/src/utilities/hooks/useScrollToTop.ts b/FrontEnd/src/utilities/hooks/useScrollToTop.ts
deleted file mode 100644
index 95c8b7b9..00000000
--- a/FrontEnd/src/utilities/hooks/useScrollToTop.ts
+++ /dev/null
@@ -1,43 +0,0 @@
-import React from "react";
-import { fromEvent } from "rxjs";
-import { filter, throttleTime } from "rxjs/operators";
-
-function useScrollToTop(
-  handler: () => void,
-  enable = true,
-  option = {
-    maxOffset: 5,
-    throttle: 1000,
-  }
-): void {
-  const handlerRef = React.useRef<(() => void) | null>(null);
-
-  React.useEffect(() => {
-    handlerRef.current = handler;
-
-    return () => {
-      handlerRef.current = null;
-    };
-  }, [handler]);
-
-  React.useEffect(() => {
-    const subscription = fromEvent(window, "scroll")
-      .pipe(
-        filter(() => {
-          return window.scrollY <= option.maxOffset;
-        }),
-        throttleTime(option.throttle)
-      )
-      .subscribe(() => {
-        if (enable) {
-          handlerRef.current?.();
-        }
-      });
-
-    return () => {
-      subscription.unsubscribe();
-    };
-  }, [enable, option.maxOffset, option.throttle]);
-}
-
-export default useScrollToTop;
-- 
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