perf[Style]: optimize the sidebar style to make it better to set (#1568)

src/styles/sidebar.scss

@@ -58,8 +58,26 @@
       width: 100% !important;
     }
 
+    // menu hover
+    .submenu-title-noDropdown,
+    .el-submenu__title {
+      &:hover {
+        background-color: $menuHover !important;
+      }
+    }
+
     .is-active>.el-submenu__title {
-      color: #f4f4f5 !important;
+      color: $subMenuActiveText !important;
+    }
+
+    & .nest-menu .el-submenu>.el-submenu__title,
+    & .el-submenu .el-menu-item {
+      min-width: $sideBarWidth !important;
+      background-color: $subMenuBg !important;
+
+      &:hover {
+        background-color: $subMenuHover !important;
+      }
     }
   }
 
@@ -108,16 +126,6 @@
     }
   }
 
-  .sidebar-container .nest-menu .el-submenu>.el-submenu__title,
-  .sidebar-container .el-submenu .el-menu-item {
-    min-width: $sideBarWidth !important;
-    background-color: $subMenuBg !important;
-
-    &:hover {
-      background-color: $menuHover !important;
-    }
-  }
-
   .el-menu--collapse .el-menu .el-submenu {
     min-width: $sideBarWidth !important;
   }
@@ -150,10 +158,19 @@
   }
 }
 
+// when menu collapsed
 .el-menu--vertical {
   &>.el-menu {
     .svg-icon {
       margin-right: 16px;
     }
   }
+
+  .nest-menu .el-submenu>.el-submenu__title,
+  .el-menu-item {
+    &:hover {
+      // You can use $subMenuHover
+      background-color: $menuHover !important;
+    }
+  }
 }

src/styles/variables.scss

@@ -9,19 +9,26 @@ $yellow:#FEC171;
 $panGreen: #30B08F;
 
 //sidebar
-$menuBg:#304156;
-$subMenuBg:#1f2d3d;
-$menuHover:#001528;
 $menuText:#bfcbd9;
 $menuActiveText:#409EFF;
+$subMenuActiveText:#f4f4f5; //https://github.com/ElemeFE/element/issues/12951
+
+$menuBg:#304156;
+$menuHover:#263445;
+
+$subMenuBg:#1f2d3d;
+$subMenuHover:#001528;
+
 $sideBarWidth: 180px;
 
 // the :export directive is the magic sauce for webpack
 :export {
+  menuText: $menuText;
+  menuActiveText: $menuActiveText;
+  subMenuActiveText: $subMenuActiveText;
   menuBg: $menuBg;
-  subMenuBg: $subMenuBg;
   menuHover: $menuHover;
-  menuText:$menuText;
-  menuActiveText:$menuActiveText;
+  subMenuBg: $subMenuBg;
+  subMenuHover: $subMenuHover;
   sideBarWidth: $sideBarWidth;
 }