gulp-xconcat

var concat = require('gulp-xconcat');
 
gulp.task('scripts', function() {
  return gulp.src('./lib/*.js')
    .pipe(concat('all.js', {
      newLine: ';',
      prefix: '// prefix...',
      suffix: '// suffix...'
    }))
    .pipe(gulp.dest('./dist/'));
});

var gulp = require('gulp');
var concat = require('gulp-xconcat');
var sourcemaps = require('gulp-sourcemaps');
 
gulp.task('javascript', function() {
  return gulp.src('src/**/*.js')
    .pipe(sourcemaps.init())
      .pipe(concat('all.js'))
    .pipe(sourcemaps.write())
    .pipe(gulp.dest('dist'));
});