title: the error with gulp browsersync
body: <p>I have some gulpfile.js below and something is wrong. To be exact, when I type gulp in terminal there comes and error:
  'browserSync' errored after 614 μs
  [20:52:42] </p>
  
  <pre><code>   TypeError: args.cb is not a function
     at Object.init 
     at Gulp.&lt;anonymous&gt; 
     at module.exports 
     at Gulp.Orchestrator._runTask 
     at Gulp.Orchestrator._runStep 
     at Gulp.Orchestrator.start 
     at Gulp.&lt;anonymous&gt; 
     at module.exports 
     at Gulp.Orchestrator._runTask 
     at Gulp.Orchestrator._runStep 
  </code></pre>
  
  <p>My gulpfile.js</p>
  
  <pre><code>            var gulp = require('gulp');
              var sass = require('gulp-sass');
              var browserSync = require('browser-sync').create();
              var reload = browserSync.reload;
              var autoprefixer = require('gulp-autoprefixer');
              var sassdoc = require('sassdoc');
              var jshint = require('gulp-jshint');
  
              var src = {
              html:['./app/index.html'],
              js:['./app/js/app.js']
              };
  
              var sassOptions = {
                  errLogToConsole: true,
                  outputStyle: 'expanded'
              };
  
              var autoprefixerOptions = {
                  browsers: ['last 15 versions', '&gt; 5%', 'Firefox ESR']
              };
  
              jshint: {
                options: {
                  node: true
                }
              }
  
              //tasks
              gulp.task('default', ['watch'], function(){
                  gulp.start('watch');
              });
  
              gulp.task('lint', function() {
                  return gulp.src('./app/js/app.js')
                          .pipe(jshint())
                          .pipe(jshint.reporter('default'));
              });
  
              gulp.task('browserSync', function() {
                  browserSync.init({
                      server: {
                          baseDir: 'app',
                          index: 'index.html'
                      },
                      port: 3000,
                      open: true
                  });
              });
  
              gulp.task('sass', function() {
                  return gulp.src('app/scss/**/*.scss')
                      .pipe(sass(sassOptions).on('error', sass.logError))
                      .pipe(autoprefixer(autoprefixerOptions))
                      .pipe(sassdoc())
                      .pipe(gulp.dest('app/css'))
                      .pipe(browserSync.reload({
                          stream: true
                      }))
              });
  
              gulp.task('html', function(){
                  gulp.src(src.html)
                      .pipe(browserSync.reload({
                          stream: true
                      }))
              });
  
              gulp.task('js', function(){
                  gulp.src(src.js)
                      .pipe(browserSync.reload({
                          stream: true
                      }))
              });
  
              gulp.task('watch', ['browserSync', 'sass'], function(){
                  gulp.watch('./app/scss/**/*.scss', ['sass']); 
                  gulp.watch('./app/**/*.html', ['html']);
                  gulp.watch('./app/js/app.js', ['js']);
                // Other watchers
              })
  </code></pre>
  
  <p>The thing is everything is working fine except it's not opening index.html file directly, just empty browser window. Can someone tell me what is wrong with the error and opening the index.html file directly?</p>