gulpfile.js

var gulp = require('gulp');
var ts = require('gulp-typescript');
var del = require('del');
var merge = require('merge-stream');
var sourcemaps = require('gulp-sourcemaps');

gulp.task('clean:output', function() {
  return del([
    'dist/*'
  ]);
});

gulp.task('watch', ['compile'], function() {
  gulp.watch([
    'bin/**/*.ts',
    'lib/**/*.ts',
    'util/**/*.ts',
    'test/**/*.ts',
    'index.ts',
    '!**/dist/*'
  ], ['compile']);
});

gulp.task('compile', ['clean:output'], function() {
  var tsProject = ts.createProject('tsconfig.json');
  var result = tsProject.src()
    .pipe(sourcemaps.init())
    .pipe(tsProject());

  var js = result.js
    .pipe(sourcemaps.write('.'))
    .pipe(gulp.dest('dist'));

  var dts = result.dts.pipe(gulp.dest('dist'));

  return merge(js, dts);
});

gulp.task('default', ['compile']);