修复误删变量定义

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@bytedo/fetch",
-  "version": "2.1.0",
+  "version": "2.1.1",
   "description": "全新的ajax封装。分2个版本, 一个基于XMLHttpRequest, 一个基于window.fetch",
   "main": "dist/index.js",
   "files": [

src/index.js

@@ -150,18 +150,19 @@ class _Request {
 
     /* --------------------------  3»» 处理跨域  --------------------- */
     try {
+      let crossDomain
       let $a = document.createElement('a')
-      $a.href = options.url
 
+      $a.href = options.url
       crossDomain = location.protocol !== $a.protocol || location.host !== $a.host
       $a = null
-    } catch (err) {}
 
-    if (crossDomain) {
-      if (options.credentials) {
-        this.xhr.withCredentials = true
+      if (crossDomain) {
+        if (options.credentials) {
+          this.xhr.withCredentials = true
+        }
       }
-    }
+    } catch (err) {}
 
     /* ------------- 4»» 根据method类型, 处理表单数据  ---------------- */