Using watchify with gulp

gulpfile.js

'use strict';

var gulp       = require('gulp');
var browserify = require('browserify');
var source     = require('vinyl-source-stream');
var notifier   = require('stream-notifier');
var watchify   = require('watchify');

gulp.task('browserify', function() {
  var bundler = browserify('./src/main')
  var bundle = compileBundle(bundler);

  return bundle();
});

gulp.task('watchify', function() {
  var opts = watchify.args;
  opts.debug = true;

  var bundler = watchify(browserify('./src/main', opts));
  var bundle = compileBundle(bundler)
  bundler.on('update', bundle);

  return bundle();
});

function compileBundle(bundler) {
  return function() {
    var n = notifier('browserify');

    return bundler
      .bundle()
      .on('error', n.error)
      .pipe(source('app.js'))
      .pipe(gulp.dest('dist'))
      .on('end', n.end);
  };
}