gulpfile.babel.js

import path from 'path';
import gulp from 'gulp';
import babel from 'gulp-babel';
import clean from 'gulp-clean';
import runSequence from 'run-sequence';
import sourcemaps from 'gulp-sourcemaps';

// Copy files other than JS
gulp.task('others', () => {
  return gulp.src(['src/**/*', '!src/**/*.js']).pipe(gulp.dest('dist'));
});

const paths = {
  sourceRoot: path.join(__dirname, 'src'),
};

// Babel JS files
gulp.task('babel', () => {
  return gulp
    .src(['src/**/*.js', '!src/**/*.test.js'])
    .pipe(sourcemaps.init())
    .pipe(babel())
    .pipe(sourcemaps.write('.', { sourceRoot: paths.sourceRoot }))
    .pipe(gulp.dest('dist'));
});

gulp.task('build-clean', () => {
  return gulp
    .src('dist')
    .pipe(clean({ force: true }))
    .pipe(gulp.dest('dist'));
});

gulp.task('build', cb => {
  return runSequence('build-clean', 'babel', 'others', cb);
});