refactor(components): use built-in methods to check for undefined and null (#20537)

style(components): check the undefined type for unification

packages/components/menu/src/menu.ts

@@ -25,6 +25,7 @@ import {
   isArray,
   isObject,
   isString,
+  isUndefined,
   mutable,
 } from '@element-plus/utils'
 import { useNamespace } from '@element-plus/hooks'
@@ -190,7 +191,7 @@ export const menuEmits = {
     isString(index) &&
     checkIndexPath(indexPath) &&
     isObject(item) &&
-    (routerResult === undefined || routerResult instanceof Promise),
+    (isUndefined(routerResult) || routerResult instanceof Promise),
 }
 export type MenuEmits = typeof menuEmits
 

packages/components/menu/src/sub-menu.ts

@@ -21,6 +21,7 @@ import {
   buildProps,
   iconPropType,
   isString,
+  isUndefined,
   throwError,
 } from '@element-plus/utils'
 import { useNamespace } from '@element-plus/hooks'
@@ -148,7 +149,7 @@ export default defineComponent({
     const isFirstLevel = computed(() => subMenu.level === 0)
     const appendToBody = computed(() => {
       const value = props.teleported
-      return value === undefined ? isFirstLevel.value : value
+      return isUndefined(value) ? isFirstLevel.value : value
     })
     const menuTransitionName = computed(() =>
       rootMenu.props.collapse

packages/components/select-v2/src/useSelect.ts

@@ -22,6 +22,7 @@ import {
   isFunction,
   isNumber,
   isObject,
+  isUndefined,
 } from '@element-plus/utils'
 import {
   useComposition,
@@ -686,7 +687,7 @@ const useSelect = (props: ISelectV2Props, emit: SelectEmitFn) => {
     if (!expanded.value) {
       return toggleMenu()
     }
-    if (hoveringIndex === undefined) {
+    if (isUndefined(hoveringIndex)) {
       hoveringIndex = states.hoveringIndex
     }
     let newIndex = -1

packages/components/tree/src/model/node.ts

@@ -75,7 +75,7 @@ const getPropertyFromData = function (node: Node, prop: string): any {
     return data[config]
   } else if (isUndefined(config)) {
     const dataProp = data[prop]
-    return dataProp === undefined ? '' : dataProp
+    return isUndefined(dataProp) ? '' : dataProp
   }
 }
 
@@ -493,7 +493,7 @@ class Node {
       children = props.children || 'children'
     }
 
-    if (data[children] === undefined) {
+    if (isUndefined(data[children])) {
       data[children] = null
     }
 

packages/components/tree/src/model/tree-store.ts

@@ -412,7 +412,7 @@ export default class TreeStore {
 
   setCurrentNodeKey(key?: TreeKey, shouldAutoExpandParent = true): void {
     this.currentNodeKey = key
-    if (key === null || key === undefined) {
+    if (isPropAbsent(key)) {
       this.currentNode && (this.currentNode.isCurrent = false)
       this.currentNode = null
       return