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https://blog.youkuaiyun.com/wangzunkuan/article/details/81242631 es5 and es6的区别
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https://www.runoob.com/jsref/prop-style-top.html 关于js中的对象问题
https://blog.youkuaiyun.com/wangzunkuan/article/details/81242631 es5 and es6的区别
es5 es5 国际标准化组织ECMA(European Computer Manufacturers Association)