gulpfile.js

const gulp = require('gulp');
const sass = require('gulp-sass');
const watch = require('gulp-watch');
const babel = require('gulp-babel');
const autoprefixer = require('gulp-autoprefixer');

// production
gulp.task('build', ['js', 'scss']);

gulp.task('js', () => {
  return gulp
    .src('src/index.js')
    .pipe(
      babel({
        presets: ['es2015', 'react', 'stage-1'],
        plugins: ['transform-runtime']
      })
    )
    .pipe(gulp.dest('dist'));
});

gulp.task('scss', () => {
  return gulp
    .src('./src/style.scss')
    .pipe(sass().on('error', sass.logError))
    .pipe(autoprefixer())
    .pipe(gulp.dest('./dist'));
});

gulp.task('dev', () => {
  gulp.watch('./src/**/*.scss', ['scss']);
  gulp.watch('./src/**/*.js', ['js']);
});