Gulpfile のひな形

const { series, parallel, watch, src, dest } = require('gulp');

const sass            = require("gulp-sass");
const packageImporter = require("node-sass-package-importer");
const autoprefixer    = require("gulp-autoprefixer");

const paths  = {
    styles :{
        src  : './src/sass/**/*.scss',
        dest : './dist/css/'
    },
    js : {
        src  : './src/js/**/*.js',
        dest : './dist/js/'
    }
}


function javascript(){
    return src(paths.js.src )
    .pipe(dest(paths.js.dest));
}

function styles(){
    return src(paths.styles.src)
    .pipe(
      sass({
        importer: packageImporter({
          extensions: [".scss", ".css"]
        })
      })
    )
    .pipe(
      autoprefixer({
        cascade: false
      })
    )
    .pipe(dest(paths.styles.dest))
}


function watchFiles(){
    watch(paths.styles.src, styles);
    watch(paths.js.src, javascript);
}

exports.default = series(parallel(styles, javascript), series(watchFiles))