Watch sass folder

gulpfile.js

const gulp = require('gulp')
const sass = require('gulp-sass')

const transpileSassToCss = (cb) => {
    return gulp.src(`src/sass/main.scss`)
        .pipe(sass())
        .pipe(gulp.dest(`src/css`))
}

const watchSassFile = () => {
    //   If you want to run the transpileSassToCss function when
    // multiple files are changed, put the file paths in the array
    return gulp.watch(['src/sass/**/*.scss'], transpileSassToCss)
    //   This glob tells gulp to watch all the files suffixed with .scss
    //   in the sass folder & in folders in the sass folder
}

exports.default = watchSassFile