

The 'this' keyword is equivalent to 'undefined' at the top level of an ES module, and has been rewritten
I am using [microbundle][1] to build the public typescript lib , when I using this `npm run build` command to build the lib,show info like this:
The 'this' keyword is equivalent to 'undefined' at the top level of an ES module, and has been rewritten
The 'this' keyword is equivalent to 'undefined' at the top level of an ES module, and has been rewritten
The 'this' keyword is equivalent to 'undefined' at the top level of an ES module, and has been rewritten
The 'this' keyword is equivalent to 'undefined' at the top level of an ES module, and has been rewritten
The 'this' keyword is equivalent to 'undefined' at the top level of an ES module, and has been rewritten
The 'this' keyword is equivalent to 'undefined' at the top level of an ES module, and has been rewritten
The 'this' keyword is equivalent to 'undefined' at the top level of an ES module, and has been rewritten
The 'this' keyword is equivalent to 'undefined' at the top level of an ES module, and has been rewritten
The 'this' keyword is equivalent to 'undefined' at the top level of an ES module, and has been rewritten
where is the problem about these info? what should I do to fix it? I have searched the whole project, and found nowhere defined the `this` keywords.
[1]: https://github.com/developit/microbundle