bundle.js

function getImportsFromFile(fileName) {
  const readline = require('readline');
  const fs = require('fs');
  const imports = [];

  return new Promise((resolve, reject) => {
    const readStream = fs.createReadStream(fileName);
    readStream.on('error', (err) => reject(err));

    const rl = readline.createInterface({input: readStream});

    rl.on('line', (line) => {
      if (line.indexOf('import') > -1) {
        const importFileName = line.match(/'(.*?)'/);
        if (importFileName) {
          imports.push(importFileName[1]);
        }
      }
    });

    rl.on('close', () => {
      resolve(imports);
    })
  });
}

async function getAllDependencies(initialFileName) {
  const orderedDependencies = [];
  const workerQueue = [initialFileName];

  try {
    while (workerQueue.length) {
      const currentFile = workerQueue.shift();
      if (orderedDependencies.indexOf(currentFile) === -1) {
        orderedDependencies.unshift(currentFile);
      }
      workerQueue.push(...await getImportsFromFile(currentFile));
    }
  } catch (err) {
    throw err;
  }

  return orderedDependencies;
}

const cliFileName = process.argv[2];

getAllDependencies(cliFileName)
  .then((result) => console.log(result))
  .catch((err) => console.log(`Derp${err}`));

Good example of Promise based read file line by line