this for ... in loop is for object, use for ... of intead

[awesomeYG]

https://github.com/sormy/flex-js/blob/951836b221e535e61ddf01738458bd74969a7e2c/src/Lexer.js#L536C1-L537C1

use for ... in loop would always get the object property like: any,select, where。 I think this is should not be there

[sormy]

We can add guard as hasOwnProperty to avoid these methods do be picked, however, there should be a good reason to do that. These any(), select(), where() look like being injected by some polyfills with imperfect implementations that is causing polyfills to pop up in for(). It is best to create unit test that fails, make a fix in the code and make failing unit test to pass.