Gulpfile.js

const gulp = require('gulp');
const sass = require('gulp-sass');
const autoprefixer = require('gulp-autoprefixer');
const browserSync = require('browser-sync').create();

gulp.task('default', ['styles'], ['lint'], function() {
  gulp.watch('sass/**/*.scss', ['styles']);
  gulp.watch('js/**/*.js', ['lint'])
  browserSync.init({
    server: './'
  });
});

task('default', () => {
    return src(['scripts/*.js'])
        // eslint() attaches the lint output to the "eslint" property
        // of the file object so it can be used by other modules.
        .pipe(eslint())
        // eslint.format() outputs the lint results to the console.
        // Alternatively use eslint.formatEach() (see Docs).
        .pipe(eslint.format())
        // To have the process exit with an error code (1) on
        // lint error, return the stream and pipe to failAfterError last.
        .pipe(eslint.failAfterError());
});

gulp.task('styles', function() {
  gulp
    .src('sass/**/*.scss')
    .pipe(sass().on('error', sass.logError))
    .pipe(
      autoprefixer({
        browsers: ['last 2 versions']
      })
    )
    .pipe(gulp.dest('./css'))
    .pipe(browserSync.stream());
});