What is wrong with my gulpfile.js?

Question

gulp.js

var gulp = require('gulp');
var less = require('gulp-less');

gulp.task('less', function() {
         return gulp.src('less/*.less')
                        .pipe(less())
                        .pipe(gulp.dest('./css'));
});

gulp.task('watch', function() {
    gulp.watch('./less/*.less', ['less']);
});

When I launch the less task, then everything is fine, when I launch the watch task, it throws an error

Answer 1

Instead of:

gulp.task('watch', function() {
    gulp.watch('./less/*.less', ['less']);
});

Did it like this:

gulp.task('watch', function() {
    gulp.watch('./less/*.less',  gulp.series('less'));
});
gulp.task('default', gulp.series('watch'));