storybook/scripts/prepublish.js

const path = require('path');
const shell = require('shelljs');
const chalk = require('chalk');
const babel = path.join(__dirname, '..', 'node_modules', '.bin', 'babel');

require('./ver');

const args = [
  '--ignore tests,__tests__,test.js,stories/,story.jsx,story.js',
  '--plugins "transform-runtime"',
  './src --out-dir ./dist',
  '--copy-files',
].join(' ');

const cmd = `${babel} ${args}`;
shell.rm('-rf', 'dist');

shell.echo(chalk.gray('\n=> Transpiling "src" into ES5 ...\n'));
shell.echo(chalk.gray(cmd));
shell.echo('');
const code = shell.exec(cmd).code;
if (code === 0) {
  shell.echo(chalk.gray('\n=> Transpiling completed.'));
} else {
  shell.exit(code);
}