优化了获取docSize 和 docScroll 方法 每次读取缓存，只有在resize 和 scroll 后才会更新缓存

src/utils/dom/document.js

@@ -1,28 +1,59 @@
-export const docScroll = {
-  get top() {
-    return document.documentElement.scrollTop || document.body.scrollTop
-  },
-  get left() {
-    return document.documentElement.scrollLeft || document.body.scrollLeft
-  },
-  set top(value) {
-    document.documentElement.scrollTop = value
-    document.body.scrollTop = value
-  },
-  set left(value) {
-    document.documentElement.scrollLeft = value
-    document.body.scrollLeft = value
-  },
-}
 
-export const docSize = {
-  get width() {
-    return document.documentElement.clientWidth || document.body.clientWidth
-  },
-  get height() {
-    return document.documentElement.clientHeight || document.body.clientHeight
-  },
-}
+export const docScroll = (function() {
+  let top
+  let left
+  const getScroll = function(e) {
+    const doc = e.target
+    top = doc.documentElement.scrollTop || doc.body.scrollTop
+    left = doc.documentElement.scrollLeft || doc.body.scrollLeft
+  }
+  window.addEventListener('DOMContentLoaded', getScroll)
+  window.addEventListener('scroll', getScroll)
+  return {
+    get top() {
+      return top
+    },
+    get left() {
+      return left
+    },
+    set top(value) {
+      document.documentElement.scrollTop = value
+      document.body.scrollTop = value
+    },
+    set left(value) {
+      document.documentElement.scrollLeft = value
+      document.body.scrollLeft = value
+    },
+    remove() {
+      window.removeEventListener('DOMContentLoaded', getScroll)
+      window.removeEventListener('scroll', getScroll)
+    },
+  }
+})()
+
+export const docSize = (function() {
+  let width
+  let height
+  const getSize = function(e) {
+    const doc = e.type === 'resize' ? e.target.document : e.target
+    width = doc.documentElement.clientWidth || doc.body.clientWidth
+    height = doc.documentElement.clientHeight || doc.body.clientHeight
+  }
+  window.addEventListener('DOMContentLoaded', getSize)
+  window.addEventListener('resize', getSize, true)
+  return {
+    get width() {
+      return width
+    },
+    get height() {
+      return height
+    },
+    remove() {
+      window.removeEventListener('DOMContentLoaded', getSize)
+      window.removeEventListener('resize', getSize)
+    },
+  }
+})()
 
 export function addEventListener(target, eventType, cb, option) {
   if (target.addEventListener) {