修复 提示条属性修改BUG；

index.html

@@ -258,7 +258,7 @@
           <p class="component-description">提供美观的下拉选择功能，支持选项分组、自定义样式和响应式设计。</p>
 
           <div class="component-demo">
-            <ui-select id="demoSelect" list="选项一,选项二,选项三" placeholder="请选择..."></ui-select>
+            <ui-select id="demoSelect" list="选项一,选项二,选项三" value="0,1,2" placeholder="请选择..."></ui-select>
             <div class="btn-group">
               <button class="btn" onclick="changeSelectOptions()">更改选项</button>
               <button class="btn" onclick="toggleSelectDisabled()">切换禁用状态</button>

index.js

@@ -382,7 +382,6 @@ class UI {
     // 下拉框
     this.Select = class Select extends HTMLElement {
       // 可用属性
-      static observedAttributes = ['placeholder', 'list', 'value', 'current', 'disabled', 'focus']
       static get observedAttributes() {
         return ['placeholder', 'list', 'value', 'current', 'disabled', 'focus']
       }
@@ -589,7 +588,7 @@ class UI {
         })
       }
     }
-    // TODO：加载中
+    // 加载中
     this.Loading = class Loading extends HTMLElement {
       static observedAttributes = ['content', 'inline', 'hidden']
       constructor() {
@@ -1374,10 +1373,12 @@ class UI {
         })
       }
     }
-    // TODO：提示条
+    // 提示条
     this.Tip = class Tip extends HTMLElement {
       // 可用属性
-      static observedAttributes = ['content', 'type', 'hidden', 'timeout']
+      static get observedAttributes() {
+        return ['content', 'type', 'hidden', 'timeout']
+      }
       constructor() {
         super()
         // 提示条
@@ -1400,15 +1401,22 @@ class UI {
       }
       // 属性变化
       attributeChangedCallback(name, oldValue, newValue) {
-        if (name == 'hidden') {
-          this[name] = newValue
-          if (this[name]) {
-            this.hide()
-          }
-        } else if (name == 'timeout') {
-          this[name] = Number(newValue)
-        } else if (name == 'type') {
-          this.Tip.className = this.Tip.part = `tip ${newValue}`
+        switch (name) {
+          case 'hidden':
+            this[name] = newValue
+            if (this[name]) {
+              this.hide()
+            }
+            break
+          case 'timeout':
+            this[name] = Number(newValue)
+            break
+          case 'type':
+            this.Tip.className = this.Tip.part = `tip ${newValue}`
+            break
+          case 'content':
+            this[name] = newValue
+            break
         }
       }
       // 初始化