* Pedantic language change
This page led to the creation of a bad question on a job interview test, leading someone to believe that functions and objects are primitives. They are not.
https://developer.mozilla.org/en-US/docs/Glossary/Primitive
* Verbiage change
1、Declare the defaultProps alone. And it is obeying AirBNB's styleguide.
2、Someone is confused about is it OK to put propTypes and defaultProps as static props inside React class. And we can explain about this question.