fix: the cache problem in tabs mode;🐛

修复：多页签模式下的缓存问题；

src/utils/util.js

@@ -0,0 +1,21 @@
+export function isDef (v){
+  return v !== undefined && v !== null
+}
+
+/**
+ * Remove an item from an array.
+ */
+export function remove (arr, item) {
+  if (arr.length) {
+    const index = arr.indexOf(item)
+    if (index > -1) {
+      return arr.splice(index, 1)
+    }
+  }
+}
+
+export function isRegExp (v) {
+  return _toString.call(v) === '[object RegExp]'
+}
+
+const _toString = Object.prototype.toString