correct-import-extensions.js

const FileHound = require('filehound');
const fs = require("fs");
const path = require("path");
const { promisify } = require("util");

FileHound.create()
  .paths("./dist")
  .discard("node_modules")
  .ext("js")
  .find()
  .then(
    async filePaths => {
      await Promise.all(
        filePaths.map(
          async filePath => {

            let contents = await promisify(fs.readFile)(
              filePath,
              "utf-8"
            );

            const statements = contents.match(/(import|export) .+ from ".+";/g);

            if (!statements) {
              return;
            }

            await Promise.all(
              statements.map(
                async statement => {
                  const url = statement.match(/"(.+)";/)[1];
                  if (url.indexOf(".") !== 0) {
                    return;
                  }
                  const [stat, indexStat] = await Promise.all([
                    promisify(fs.stat)(path.resolve(path.dirname(filePath), url + ".js")).catch(() => {}),
                    promisify(fs.stat)(path.resolve(path.dirname(filePath), url + "/index.js")).catch(() => {})
                  ]);
                  if (stat && stat.isFile()) {
                    contents = contents.replace(
                      statement,
                      statement.replace(url, url + ".js")
                    );
                  } else if (indexStat && indexStat.isFile()) {
                    contents = contents.replace(
                      statement,
                      statement.replace(url, url + "/index.js")
                    );
                  }
                }
              )
            );

            await promisify(fs.writeFile)(filePath, contents, "utf-8");

          }
        )
      )
    }
  )
  .then(() => console.log("Complete"))
  .catch(error => console.error(error));