diff --git a/build.js b/build.js
index f62df39..c28062b 100644
--- a/build.js
+++ b/build.js
@@ -6,20 +6,10 @@
 
 const Es = require('esbuild')
 
-Es.build({
-  entryPoints: ['src/index.mjs'],
-  outfile: 'dist/index.mjs',
-  platform: 'node',
-  bundle: true,
-  minify: true,
-  format: 'esm'
-})
-
 Es.build({
   entryPoints: ['src/index.mjs'],
   outfile: 'dist/index.js',
-  platform: 'node',
   minify: true,
   bundle: true,
-  target: 'node8'
+  target: 'es6'
 })
diff --git a/package.json b/package.json
index 65f5bfc..5095307 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "es.shim",
-  "version": "2.1.1",
+  "version": "2.2.0",
   "description": "实现部分新API, 以及一些常用的扩展方法",
   "keyworks": [
     "es5",
diff --git a/src/lib/date.js b/src/lib/date.js
index 3375e7a..07f7077 100644
--- a/src/lib/date.js
+++ b/src/lib/date.js
@@ -6,7 +6,7 @@
 //获取当天是本月第几周
 if (!Date.isDate) {
   Object.defineProperty(Date, 'isDate', {
-    value: function(obj) {
+    value: function (obj) {
       return obj && typeof obj === 'object' && obj.getTime ? true : false
     },
     writable: true
@@ -16,7 +16,7 @@ if (!Date.isDate) {
 if (!Date.prototype.getFullWeek) {
   //获取当天是本年度第几周
   Object.defineProperty(Date.prototype, 'getFullWeek', {
-    value: function() {
+    value: function () {
       let thisYear = this.getFullYear()
       let that = new Date(thisYear, 0, 1)
       let firstDay = that.getDay()
@@ -27,7 +27,7 @@ if (!Date.prototype.getFullWeek) {
 
   //获取当天是本月第几周
   Object.defineProperty(Date.prototype, 'getWeek', {
-    value: function() {
+    value: function () {
       let today = this.getDate()
       let thisMonth = this.getMonth()
       let thisYear = this.getFullYear()
@@ -40,8 +40,8 @@ if (!Date.prototype.getFullWeek) {
 //时间格式化
 if (!Date.prototype.format) {
   Object.defineProperty(Date.prototype, 'format', {
-    value: function(str) {
-      var dt = {
+    value: function (str) {
+      let dt = {
         fullyear: this.getFullYear(),
         year: this.getYear(),
         fullweek: this.getFullWeek(),
@@ -53,7 +53,7 @@ if (!Date.prototype.format) {
         minutes: this.getMinutes(),
         seconds: this.getSeconds()
       }
-      var reg = null
+      let reg = null
 
       str = str || 'Y-m-d H:i:s'
       dt.g = dt.hours > 12 ? dt.hours - 12 : dt.hours
diff --git a/src/lib/object.js b/src/lib/object.js
index 8482d85..293935c 100644
--- a/src/lib/object.js
+++ b/src/lib/object.js
@@ -28,7 +28,7 @@ if (!Object.empty) {
 if (!Object.prototype.toParams) {
   Object.defineProperty(Object.prototype, 'toParams', {
     value: function () {
-      var params = ''
+      let params = ''
       for (let k in this) {
         if (this[k] === void 0) {
           continue
diff --git a/src/lib/string.js b/src/lib/string.js
index edd0c34..a450cd7 100644
--- a/src/lib/string.js
+++ b/src/lib/string.js
@@ -127,7 +127,7 @@ if (!String.prototype.escape) {
 if (!String.prototype.at) {
   Object.defineProperty(String.prototype, 'at', {
     value: function (num) {
-      var n = +num
+      let n = +num
       if (n < 0) {
         n += this.length
       }
@@ -144,12 +144,12 @@ if (!String.prototype.at) {
 if (!String.prototype.toJson) {
   Object.defineProperty(String.prototype, 'toJson', {
     value: function () {
-      var str = this.replace(/^\?/, '')
-      var params = decodeURIComponent(str)
+      let str = this.replace(/^\?/, '')
+      let params = decodeURIComponent(str)
         .split('&')
         .filter(_ => _)
         .map(_ => _.split('='))
-      var obj = {}
+      let obj = {}
       for (let it of params) {
         obj[it[0]] = it[1] || ''
       }