gulpfile.js

var gulp          = require('gulp');
var concat        = require('gulp-concat');
var browserSync   = require("browser-sync").create();
var sourcemaps    = require('gulp-sourcemaps');
var pipeline      = require('readable-stream').pipeline;
var terser        = require('gulp-terser');

// concatenate all the files
gulp.task('concat', function() {
  return pipeline(
    gulp.src(['./js/*.js', './lib/*.js', '!lib/glpk.min.js', '!js/worker.js']),
    sourcemaps.init(),
    terser(),
    concat('dist.js'),
    sourcemaps.write(),
    gulp.dest('./dist/')
  )
});

// serve page from root folder, go directly to docs
gulp.task('serve', function() {
  browserSync.init({
      server: {
          baseDir: "./",
        //   middleware: [{
        //   route: "/",
        //   // handle: (req, res, next) => {
        //   //   res.writeHead(302,  { 'Location': '/' })
        //   //   res.end()
        //   //   next()
        //   // }
        // }]
      }
  });
});

// watch js and html files, reload when something changes
gulp.task('watch', function() {
  gulp.watch(
    ['./js/*.js', './lib/*.js', './*.html'],
    gulp.parallel('concat')
  );
  // browserSync.reload();
});

// default task
gulp.task('default', gulp.parallel('concat', 'serve', 'watch'));