Fair enough, just keep in mind that documentation is different from comments.
I would just like to add something you might be interested in.
If you wanted your function "longestString" to be available outside of its package as a library function for example, you would want to comment using jsdoc.
More than it allows you to generate an html doc form your code, your IDE knows about jsdoc and can generate friendly popup as you try to use this function.
Have a look at the difference:
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