Gulp v4 doesn't update the browser

Question

When I start gulp Google Chrome doesn't open my http://localhost:3000 and doesn't update my css file automaticaly. I have no idea what am I doing wrong.

It's my first time using Gulp, guys. Any idea to fix it? Thanks

var gulp = require('gulp')
var browserSync = require('browser-sync').create()
var sass = require('gulp-sass')

//compile sass
gulp.task('sass', function() {
    return gulp.src(['node_modules/bootstrap/scss/bootstrap.scss', 'src/scss/*.scss'])
    .pipe(sass())
    .pipe(gulp.dest("src/css"))
    .pipe(browserSync.stream())
})

//move js to src/js
gulp.task('js', function(){
    return gulp.src(['node_modules/bootstrap/dist/js/bootstrap.min.js', 'node_modules/jquery/dist/jquery.min.js',
    'node_modules/popper.js/dist/umd/popper.min.js'])
    .pipe(gulp.dest("src/js"))
    .pipe(browserSync.stream())
})

//gulp html and scss
gulp.task('serve', gulp.parallel('sass'), function(){
    browserSync.init({
        server: "./src"
    })

    gulp.watch(['node_modules/bootstrap/scss/bootstrap.scss', 'src/scss/*.scss'], ['sass'])
    gulp.watch("src/*.html").on('change', browserSync.reload)
})

gulp.task('default', gulp.series('js', 'serve'))

Answer 1

Change this line:

gulp.watch(['node_modules/bootstrap/scss/bootstrap.scss', 'src/scss/*.scss'], ['sass'])

to

gulp.watch(['node_modules/bootstrap/scss/bootstrap.scss', 'src/scss/*.scss'], gulp.series('sass'))

Your version was gulp v3, not gulp v4.

Also I would change

gulp.task('default', gulp.series('js', 'serve'))

to

gulp.task('default', gulp.series('js', 'sass', 'serve'))

so that you can simplify to:

gulp.task('serve', function(){ // removed the parallel part.

The first time you run gulp.default you may need refresh the browser if you have some changes already made to your files. Best to start the default task first and then make changes to your files.