New top story on Hacker News: Ask HN: What are the ways you go about getting comfortable with a new codebase?

Ask HN: What are the ways you go about getting comfortable with a new codebase?
23 by jarusll | 29 comments on Hacker News.
Tools like Eclipse's Java Browsing Perspective(https://ift.tt/qoKQPBY), Visual Studio's Object Browser make it easier to browse the codebase by components. What are the ways you do it? Is there anything similar available for functional programming?