diff --git a/src/PortalWrapper.tsx b/src/PortalWrapper.tsx
index a1fe81c6..a5fa3555 100644
--- a/src/PortalWrapper.tsx
+++ b/src/PortalWrapper.tsx
@@ -17,7 +17,7 @@ export function getOpenCount() {
 
 // https://github.com/ant-design/ant-design/issues/19340
 // https://github.com/ant-design/ant-design/issues/19332
-let cacheOverflow = {};
+let cacheOverflow: React.CSSProperties = {};
 
 const getParent = (getContainer: GetContainer) => {
   if (!supportDom) {
diff --git a/src/getScrollBarSize.tsx b/src/getScrollBarSize.tsx
index 77092c06..35709437 100644
--- a/src/getScrollBarSize.tsx
+++ b/src/getScrollBarSize.tsx
@@ -68,11 +68,12 @@ ${heightStyle}
 
   // Measure. Get fallback style if provided
   const scrollWidth =
-    ele && fallbackWidth && !isNaN(fallbackWidth)
+    ele && fallbackWidth && !Number.isNaN(fallbackWidth)
       ? fallbackWidth
       : measureEle.offsetWidth - measureEle.clientWidth;
+
   const scrollHeight =
-    ele && fallbackHeight && !isNaN(fallbackHeight)
+    ele && fallbackHeight && !Number.isNaN(fallbackHeight)
       ? fallbackHeight
       : measureEle.offsetHeight - measureEle.clientHeight;
 
diff --git a/src/isMobile.ts b/src/isMobile.ts
index 05b94d62..7bb3c2ff 100644
--- a/src/isMobile.ts
+++ b/src/isMobile.ts
@@ -2,10 +2,11 @@ import isMobile from 'is-mobile';
 
 let cached: boolean;
 
-export default () => {
+const getIsMobile = () => {
   if (typeof cached === 'undefined') {
     cached = isMobile();
   }
-
   return cached;
 };
+
+export default getIsMobile;