fix[MockJS]: fix bug with withCredentials after using mockjs (#1194)

* 修复 Mock 导致请求丢失 Cookie 的问题

修复 Mock 导致 Cookie 丢失的问题，只有在 XHR.open() 周期时，自定义的 withCredentials 会被挂载，此时检查是否是未被拦截的 xhr，并挂载自定义的 withCredentials ，无则默认为 false

src/mock/index.js

@@ -4,6 +4,16 @@ import articleAPI from './article'
 import remoteSearchAPI from './remoteSearch'
 import transactionAPI from './transaction'
 
+// 修复在使用 MockJS 情况下，设置 withCredentials = true，且未被拦截的跨域请求丢失 Cookies 的问题
+// https://github.com/nuysoft/Mock/issues/300
+Mock.XHR.prototype.proxy_send = Mock.XHR.prototype.send
+Mock.XHR.prototype.send = function() {
+  if (this.custom.xhr) {
+    this.custom.xhr.withCredentials = this.withCredentials || false
+  }
+  this.proxy_send(...arguments)
+}
+
 // Mock.setup({
 //   timeout: '350-600'
 // })