Javascript Documentation Generation

February 3, 2015

I have always been trying to find a good Javascript documentation generator and I have never really been very happy with any that I have found. So I’ve decided to just write my own, DocAST.

The problem I have always had with any documentation generators is they are either hard to theme or are sometimes very strict with the way doc strings are suppose to be written, making them potentially difficult to switch between documentation generators if you had to. So for a fun exercise I’ve decided to just try writting one myself, DocAST.

What is different about DocAST? I’ve seen a few documentation parsers which use regular expressions to parse out the comment blocks, which works perfectly well, except I’ve decided to have some fun and use AST parsing to grab the code blocks from the scripts. As well, DocAST doesn’t try to force you in to any specific theme or display, instead it is used simply to extract documentation from scripts. Lastly, DocAST, doesn’t use any specific documentation format for signifying parameters, returns or exceptions, it will traverse the AST of the code block to find them for you, so most of the time you just need to add a simple block comment describing the function above it.

Lets just get to an example:

// script.js

 * This is my super cool function that does all sorts of cool stuff
function superCool(arg1, arg2){
    if(arg1 === arg2){
        throw new Exception("arg1 and arg2 cant be the same");

    var sum = arg1 + arg2;
    return sum;
$ docast extract ./script.js
$ cat out.json
        "name": "superCool",
        "params": [
        "returns": [
        "raises": [
        "doc": " This is my super cool function that does all sorts of cool stuff\n"

For more information check out the github page for DocAST.

The other benefit I have found with a documentation parser (something that just extracts the documentation information as opposed to trying to build it) is that you can get fun and creative with how you use the information parsed. For example, I’ve had someone suggest creating your doc strings as yaml. When you parse out the string just parse the yaml to get an object which is then easy to pass on to jade or some other templating engine to generate your documentation. If you want to see an example of this, just check out the documentation for DocAST and the code used to generate the docs at

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