gulp with javascript concatenation

gulpfile.js

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

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

gulp.task('scripts', function() {
  return gulp.src('src/**/*.js')
    .pipe(concat('app.js'))
    .pipe(gulp.dest('dist'));
});

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