[Doc] Stepper: optimize async demo (#3098)

packages/stepper/demo/index.vue

@@ -51,9 +51,16 @@ export default {
       stepper3: null
     };
   },
+
   methods: {
     onChange(value) {
+      if (this.changing) {
+        return;
+      }
+
+      this.changing = true;
       setTimeout(() => {
+        this.changing = false;
         this.stepper2 = value;
       }, 500);
     }

packages/stepper/en-US.md

@@ -51,8 +51,14 @@ export default {
 
   methods: {
     onChange(value) {
+      if (this.changing) {
+        return;
+      }
+
+      this.changing = true;
       setTimeout(() => {
         this.value = value;
+        this.changing = false;
       }, 500);
     }
   }

packages/stepper/zh-CN.md

@@ -53,8 +53,14 @@ export default {
 
   methods: {
     onChange(value) {
+      if (this.changing) {
+        return;
+      }
+
+      this.changing = true;
       setTimeout(() => {
         this.value = value;
+        this.changing = false;
       }, 500);
     }
   }