Extract functions from js source code

extract-functions.js

import { opendir, readFile } from 'fs/promises';
import { join } from 'path'
import * as parser from "@babel/parser";
import _traverse from "@babel/traverse";
const traverse = _traverse.default;


for await (const file of allFiles('javascript')) {
  if (file.endsWith('.js')) {
    const buffer = await readFile(file)
    const code = buffer.toString()

    for (const fn of extractFunctions(code)) {

      // Print function to each line
      console.log(JSON.stringify(fn))
      
      // You could upload to a db here instead
    }
  }
}


/** recursively get all files */
async function* allFiles(directory) {
  for await (const file of await opendir(directory)) {
    const path = join(directory, file.name)

    if (file.isFile()) {
      yield path
    }

    if (file.isDirectory()) {
      for await (const entry of allFiles(path)) {
        yield entry;
      }
    }
  }
}

/** Find function definitions from a js file string */
function extractFunctions(code) {
  try {
    const fns = []
    const ast = parser.parse(code, { sourceType: "module" })

    traverse(ast, {
      enter({ node: { type, start, end } }) {
        if (type === 'FunctionDeclaration') {
          fns.push(code.slice(start, end))
        }
      }
    })

    return fns;
  } catch {
    return []
  }
}