Have a look at https://github.com/scottrogowski/code2flow for generating callgraphs.
Code2flow will sweep through your project source code looking for function definitions. Then it will do another sweep looking for where those functions are called. Code2flow connects the dots and presents you with a flowchart estimating the functional structure of your program.
In other words, code2flow generates callgraphs
I recommend using an IDE such as WebStorm or Eclipse. You will be able to rename variables and functions, navigate to definitions and find cross-references.