text: const del = require('del');
  const gulp = require("gulp");
  const babel = require("gulp-babel");
  const concat = require("gulp-concat");
  const sequence = require('run-sequence').use(gulp);
  
  const dest = './dist/'
  const artifact = 'csl.js';
  
  gulp.task('clear', () => {
      return del([dest + artifact, 'index.js']);
  });
  
  gulp.task('pack', function() {
      return gulp.src(["src/CSLUtility.js", "src/CSLMessage.js", "src/polyfill.js"])
          .pipe(babel())
          .pipe(concat(artifact))
          .pipe(gulp.dest(dest));
  });
  
  gulp.task('export', function() {
      return gulp.src(["src/CSLUtility.js", "src/CSLMessage.js", "src/export.js"])
          .pipe(concat('index.js'))
          .pipe(gulp.dest('./'));
  });
  
  gulp.task('default', callback => {
      sequence(
          'clear',
          'pack',
          'export',
          callback
      );
  });