290 doc js classes

[evolvingkid]

Pull Request Template

Description

Add a new content for JavaScript. The content is about classes in JavaScript. The changes are with the issues #290

How Has This Been Tested?

Tested with simple qa testing doing the test case.

Checklist:

• [ ] My code follows the style guidelines of this project
• [ ] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] New and existing unit tests pass locally with my changes
• [ ] Any dependent changes have been merged and published in downstream modules
• [ ] I have checked my code and corrected any misspellings