diff --git a/examples/formError.js b/examples/formError.js
index 02c4487..762ca0d 100644
--- a/examples/formError.js
+++ b/examples/formError.js
@@ -1,44 +1,43 @@
-'use strict';
 
 import React from 'react';
 import ReactDOM from 'react-dom';
 import Tooltip from 'rc-tooltip';
 import 'rc-tooltip/assets/bootstrap.less';
 
-var Test = React.createClass({
+const Test = React.createClass({
   getInitialState() {
     return {
-      visible: false
+      visible: false,
     };
   },
-  handleDestroy(){
+  handleDestroy() {
     this.setState({
-      destroy:true
+      destroy: true,
     });
   },
-  handleChange(e){
+  handleChange(e) {
     this.setState({
-      visible:!e.target.value
+      visible: !e.target.value,
     });
   },
   render() {
-    if(this.state.destroy){
+    if (this.state.destroy) {
       return null;
     }
-    return <div >
+    return (<div>
       <div style={{marginTop: 100, marginLeft: 100, marginBottom: 100}}>
         <Tooltip
           visible={this.state.visible}
           animation="zoom"
           trigger={[]}
-          overlayStyle={{zIndex:1000}}
+          overlayStyle={{zIndex: 1000}}
           overlay={<span>required!</span>}>
           <input onChange={this.handleChange}/>
         </Tooltip>
       </div>
       <button onClick={this.handleDestroy}>destroy</button>
-    </div>;
-  }
+    </div>);
+  },
 });
 
-ReactDOM.render(<Test/>, document.getElementById("__react-content"));
+ReactDOM.render(<Test/>, document.getElementById('__react-content'));
diff --git a/examples/handleVisibleChange.js b/examples/handleVisibleChange.js
index b4232d9..8427175 100644
--- a/examples/handleVisibleChange.js
+++ b/examples/handleVisibleChange.js
@@ -1,31 +1,34 @@
-'use strict';
 
 import React from 'react';
 import ReactDOM from 'react-dom';
 import Tooltip from 'rc-tooltip';
 import 'rc-tooltip/assets/bootstrap.less';
 
-var Test = React.createClass({
+function preventDefault(e) {
+  e.preventDefault();
+}
+
+const Test = React.createClass({
   getInitialState() {
     return {
-      visible: false
+      visible: false,
     };
   },
   handleVisibleChange(visible) {
     this.setState({
-      visible: visible
+      visible: visible,
     });
   },
-  handleDestroy(){
+  handleDestroy() {
     this.setState({
-      destroy:true
+      destroy: true,
     });
   },
   render() {
-    if(this.state.destroy){
+    if (this.state.destroy) {
       return null;
     }
-    return <div >
+    return (<div>
       <div style={{marginTop: 300, marginLeft: 100, marginBottom: 100}}>
         <Tooltip
           visible={this.state.visible}
@@ -33,16 +36,12 @@ var Test = React.createClass({
           onVisibleChange={this.handleVisibleChange}
           trigger="click"
           overlay={<span>i am a tooltip</span>}>
-          <a href='#' onClick={preventDefault}>trigger</a>
+          <a href="#" onClick={preventDefault}>trigger</a>
         </Tooltip>
       </div>
       <button onClick={this.handleDestroy}>destroy</button>
-    </div>;
-  }
+    </div>);
+  },
 });
 
-function preventDefault(e) {
-  e.preventDefault();
-}
-
-ReactDOM.render(<Test/>, document.getElementById("__react-content"));
+ReactDOM.render(<Test/>, document.getElementById('__react-content'));
diff --git a/examples/placement.js b/examples/placement.js
index 23acff7..368ec30 100644
--- a/examples/placement.js
+++ b/examples/placement.js
@@ -1,13 +1,10 @@
-'use strict';
 
 import React from 'react';
 import ReactDOM from 'react-dom';
 import Tooltip from 'rc-tooltip';
 import 'rc-tooltip/assets/bootstrap.less';
 const text = <span>提示文字</span>;
-
-var A = (props)=> {
-  return <a {...props} style={{
+const styles = {
   display: 'inline-block',
   lineHeight: '40px',
   height: '40px',
@@ -17,56 +14,51 @@ var A = (props)=> {
   marginRight: '1em',
   marginBottom: '1em',
   borderRadius: '6px',
-  }}/>
 };
 
-var Test = React.createClass({
+const Test = React.createClass({
   render() {
-    return <div>
+    return (<div>
       <Tooltip placement="left" overlay={text}>
-        <A href="#">左边</A>
+        <a href="#" style={styles}>左边</a>
       </Tooltip>
       <Tooltip placement="top" overlay={text}>
-        <A href="#">上边</A>
+        <a href="#" style={styles}>上边</a>
       </Tooltip>
       <Tooltip placement="bottom" overlay={text}>
-        <A href="#">下边</A>
+        <a href="#" style={styles}>下边</a>
       </Tooltip>
       <Tooltip placement="right" overlay={text}>
-        <A href="#">右边</A>
+        <a href="#" style={styles}>右边</a>
       </Tooltip>
       <br />
       <Tooltip placement="leftTop" overlay={text}>
-        <A href="#">左上</A>
+        <a href="#" style={styles}>左上</a>
       </Tooltip>
       <Tooltip placement="leftBottom" overlay={text}>
-        <A href="#">左下</A>
+        <a href="#" style={styles}>左下</a>
       </Tooltip>
       <Tooltip placement="rightTop" overlay={text}>
-        <A href="#">右上</A>
+        <a href="#" style={styles}>右上</a>
       </Tooltip>
       <Tooltip placement="rightBottom" overlay={text}>
-        <A href="#">右下</A>
+        <a href="#" style={styles}>右下</a>
       </Tooltip>
       <br />
       <Tooltip placement="topLeft" overlay={text}>
-        <A href="#">上左</A>
+        <a href="#" style={styles}>上左</a>
       </Tooltip>
       <Tooltip placement="topRight" overlay={text}>
-        <A href="#">上右</A>
+        <a href="#" style={styles}>上右</a>
       </Tooltip>
       <Tooltip placement="bottomLeft" overlay={text}>
-        <A href="#">下左</A>
+        <a href="#" style={styles}>下左</a>
       </Tooltip>
       <Tooltip placement="bottomRight" overlay={text}>
-        <A href="#">下右</A>
+        <a href="#" style={styles}>下右</a>
       </Tooltip>
-    </div>;
-  }
+    </div>);
+  },
 });
 
-function preventDefault(e) {
-  e.preventDefault();
-}
-
-ReactDOM.render(<Test/>, document.getElementById("__react-content"));
+ReactDOM.render(<Test/>, document.getElementById('__react-content'));
diff --git a/examples/simple.js b/examples/simple.js
index 5580532..86a0d74 100644
--- a/examples/simple.js
+++ b/examples/simple.js
@@ -1,4 +1,3 @@
-'use strict';
 
 import React from 'react';
 import ReactDOM from 'react-dom';
@@ -9,15 +8,15 @@ import assign from 'object-assign';
 // do not use rc-tooltip/lib/placements
 import placements from 'rc-tooltip/src/placements';
 
-var Test = React.createClass({
+const Test = React.createClass({
   getInitialState() {
-    const placement='right';
+    const placement = 'right';
     const offset = placements[placement].offset;
     return {
-      destroyTooltipOnHide:false,
+      destroyTooltipOnHide: false,
       placement: placement,
       trigger: {
-        hover: 1
+        hover: 1,
       },
       offsetX: offset[0],
       offsetY: offset[1],
@@ -35,66 +34,66 @@ var Test = React.createClass({
 
   onTransitionChange(e) {
     this.setState({
-      transitionName: e.target.checked ? e.target.value : ''
+      transitionName: e.target.checked ? e.target.value : '',
     });
   },
 
   onTriggerChange(e) {
-    var trigger = assign({}, this.state.trigger);
+    const trigger = assign({}, this.state.trigger);
     if (e.target.checked) {
       trigger[e.target.value] = 1;
     } else {
       delete trigger[e.target.value];
     }
     this.setState({
-      trigger: trigger
+      trigger: trigger,
     });
   },
 
   onOffsetXChange(e) {
-    var targetValue = e.target.value;
+    const targetValue = e.target.value;
     this.setState({
       offsetX: targetValue ? targetValue : undefined,
     });
   },
 
   onOffsetYChange(e) {
-    var targetValue = e.target.value;
+    const targetValue = e.target.value;
     this.setState({
       offsetY: targetValue ? targetValue : undefined,
     });
   },
 
-  preventDefault(e) {
-    e.preventDefault();
-  },
-
   onVisibleChange(visible) {
     console.log('tooltip', visible);
   },
 
   onDestroyCheck() {
     this.setState({
-      destroyTooltipOnHide: !this.state.destroyTooltipOnHide
+      destroyTooltipOnHide: !this.state.destroyTooltipOnHide,
     });
   },
 
+  preventDefault(e) {
+    e.preventDefault();
+  },
+
   render() {
-    var state = this.state;
-    var trigger = state.trigger;
-    return <div >
+    const state = this.state;
+    const trigger = state.trigger;
+    return (<div>
       <div style={{margin: '10px 20px'}}>
         <label>
           placement:
           <select value={this.state.placement} onChange={this.onPlacementChange}>
-            {Object.keys(placements).map(function (p) {
-              return <option key={p} value={p}>{p}</option>
+            {Object.keys(placements).map(function(p) {
+              return <option key={p} value={p}>{p}</option>;
             })}
           </select>
         </label>
         &nbsp;&nbsp;&nbsp;&nbsp;
         <label>
-          <input value='rc-tooltip-zoom' type='checkbox' onChange={this.onTransitionChange}
+          <input value="rc-tooltip-zoom" type="checkbox" onChange={this.onTransitionChange}
                  checked={this.state.transitionName === 'rc-tooltip-zoom'}/>
           transitionName
         </label>
@@ -102,7 +101,7 @@ var Test = React.createClass({
         &nbsp;&nbsp;&nbsp;&nbsp;
 
         <label>
-          <input  type='checkbox' onChange={this.onDestroyCheck}
+          <input type="checkbox" onChange={this.onDestroyCheck}
                  checked={this.state.destroyTooltipOnHide}/>
           destroyTooltipOnHide
         </label>
@@ -112,26 +111,26 @@ var Test = React.createClass({
         trigger:
 
         <label>
-          <input value='hover' checked={trigger.hover} type='checkbox' onChange={this.onTriggerChange}/>
+          <input value="hover" checked={trigger.hover} type="checkbox" onChange={this.onTriggerChange}/>
           hover
         </label>
         <label>
-          <input value='focus' checked={trigger.focus} type='checkbox' onChange={this.onTriggerChange}/>
+          <input value="focus" checked={trigger.focus} type="checkbox" onChange={this.onTriggerChange}/>
           focus
         </label>
         <label>
-          <input value='click' checked={trigger.click} type='checkbox' onChange={this.onTriggerChange}/>
+          <input value="click" checked={trigger.click} type="checkbox" onChange={this.onTriggerChange}/>
           click
         </label>
         <br/>
         <label>
           offsetX:
-          <input type='text' value={state.offsetX} onChange={this.onOffsetXChange} style={{width:50}}/>
+          <input type="text" value={state.offsetX} onChange={this.onOffsetXChange} style={{width: 50}}/>
         </label>
         &nbsp;&nbsp;&nbsp;&nbsp;
         <label>
           offsetY:
-          <input type='text' value={state.offsetY} onChange={this.onOffsetYChange} style={{width:50}}/>
+          <input type="text" value={state.offsetY} onChange={this.onOffsetYChange} style={{width: 50}}/>
         </label>
       </div>
       <div style={{margin: 100}}>
@@ -141,18 +140,18 @@ var Test = React.createClass({
                  destroyTooltipOnHide={this.state.destroyTooltipOnHide}
                  trigger={Object.keys(this.state.trigger)}
                  onVisibleChange={this.onVisibleChange}
-                 overlay={<div style={{height:50,width:50}}>i am a tooltip</div>}
+                 overlay={<div style={{height: 50, width: 50}}>i am a tooltip</div>}
                  align={{
-                  offset:[this.state.offsetX, this.state.offsetY]
+                   offset: [this.state.offsetX, this.state.offsetY],
                  }}
                  transitionName={this.state.transitionName}>
-          <div style={{height:100,width:100,border:'1px solid red'}}>trigger</div>
+          <div style={{height: 100, width: 100, border: '1px solid red'}}>trigger</div>
         </Tooltip>
       </div>
-    </div>;
-  }
+    </div>);
+  },
 });
 
 ReactDOM.render(<div>
   <Test />
-</div>, document.getElementById("__react-content"));
+</div>, document.getElementById('__react-content'));
diff --git a/package.json b/package.json
index e98615a..78d7563 100644
--- a/package.json
+++ b/package.json
@@ -45,6 +45,7 @@
     "bootstrap": "~3.3.2",
     "expect.js": "~0.3.1",
     "jquery": "~1.11.2",
+    "object-assign": "~4.0.1",
     "precommit-hook-eslint": "3.x",
     "rc-server": "3.x",
     "rc-tools": "4.x",
diff --git a/tests/index.spec.js b/tests/index.spec.js
index 38aa0d9..d3a37a1 100644
--- a/tests/index.spec.js
+++ b/tests/index.spec.js
@@ -1,26 +1,24 @@
-'use strict';
 
-var expect = require('expect.js');
-var React = require('react');
-var ReactDOM = require('react-dom');
-var TestUtils = require('react-addons-test-utils');
-var Simulate = TestUtils.Simulate;
-var $ = require('jquery');
+import '../assets/bootstrap.less';
+import expect from 'expect.js';
+import React from 'react';
+import ReactDOM from 'react-dom';
+import TestUtils from 'react-addons-test-utils';
+import $ from 'jquery';
+import Tooltip from '../index';
+import async from 'async';
 window.$ = $;
-require('../assets/bootstrap.less');
-var Tooltip = require('../index');
-var scryRenderedDOMComponentsWithClass = TestUtils.scryRenderedDOMComponentsWithClass;
-var async = require('async');
+const Simulate = TestUtils.Simulate;
 
 function timeout(ms) {
   return (done)=> {
     setTimeout(done, ms);
-  }
+  };
 }
 
-describe('rc-tooltip', function () {
+describe('rc-tooltip', function() {
   this.timeout(40000);
-  var div = document.createElement('div');
+  const div = document.createElement('div');
   div.style.margin = '100px';
   document.body.insertBefore(div, document.body.firstChild);
 
@@ -30,21 +28,21 @@ describe('rc-tooltip', function () {
 
   describe('trigger', ()=> {
     it('works', (done)=> {
-      var tooltip = ReactDOM.render(<Tooltip trigger={['click']}
+      const tooltip = ReactDOM.render(<Tooltip trigger={['click']}
                                              placement="left"
-                                             overlay={<strong className='x-content'>tooltip2</strong>}>
+                                             overlay={<strong className="x-content">tooltip2</strong>}>
         <div className="target">click</div>
       </Tooltip>, div);
-      var domNode = ReactDOM.findDOMNode(tooltip);
+      const domNode = ReactDOM.findDOMNode(tooltip);
       Simulate.click(domNode);
       async.series([timeout(20), (next)=> {
-        var popupDomNode = tooltip.getPopupDomNode();
+        const popupDomNode = tooltip.getPopupDomNode();
         expect($(popupDomNode).find('.x-content').html()).to.be('tooltip2');
         expect(popupDomNode).to.be.ok();
         Simulate.click(domNode);
         next();
       }, timeout(20), (next)=> {
-        var popupDomNode = tooltip.getPopupDomNode();
+        const popupDomNode = tooltip.getPopupDomNode();
         expect($(popupDomNode).css('display')).to.be('none');
         next();
       }], done);