Typescript, watchify, gulp - minimal conf with error logging on the console

gulpfile.js

var gulp = require('gulp');
var ts = require('gulp-typescript');
var browserify = require("browserify");
var source = require('vinyl-source-stream');
var watchify = require("watchify");
var tsify = require("tsify");
var gutil = require("gulp-util");

gulp.task('typescript', function () {
    return gulp.src('./app/src/**/*.ts')
        .pipe(ts())
        .pipe(gulp.dest('./app/dist'));
});

var watchedBrowserify = watchify(browserify({
    basedir: '.',
    debug: true,
    entries: ['app/src/main.ts'],
    cache: {},
    packageCache: {}
}).plugin(tsify));


function bundle() {
    return watchedBrowserify
        .bundle()
        .on("error", gutil.log)
        .pipe(source('main.js'))
        .pipe(gulp.dest("app/dist"));
}

gulp.task("default", bundle);

watchedBrowserify.on("update", bundle);
watchedBrowserify.on("log", gutil.log);