Gulpfile.js

var gulp       = require('gulp'),
    typescript = require('gulp-typescript'),
    sass       = require('gulp-sass'),
    concat     = require('gulp-concat'),
    livereload = require('gulp-livereload'),
    http       = require('http'),
    st         = require('st');

gulp.task('scripts', function () {
  gulp
    .src('./src/scripts/*.ts')
    .pipe(concat('main.ts'))
    .pipe(typescript({ declarationFiles: true }))
    .pipe(gulp.dest('./build/scripts/'))
    .pipe(livereload());
});

gulp.task('views', function () {
  gulp
    .src('./src/*.html')
    .pipe(gulp.dest('./build/'))
    .pipe(livereload());
});

gulp.task('styles', function () {
  gulp
    .src('./src/styles/*.scss')
    .pipe(sass())
    .pipe(concat('style.css'))
    .pipe(gulp.dest('./build/styles'))
    .pipe(livereload());
});

gulp.task('watch', ['build'], function (done) {

  livereload.listen();

  http.createServer(
    st({
      path:  __dirname + '/build/',
      cache: false
    })
  ).listen(8080, done);

  gulp.watch('./src/scripts/*', ['scripts']);
  gulp.watch('./src/styles/*', ['styles']);
  gulp.watch('./src/*.html', ['views']);
});

gulp.task('build', ['scripts', 'views', 'styles']);
gulp.task('default', ['build']);