a gulp extend

watcher.js

var through = require('through');
var gutil = require('gulp-util');
var path = require('path');

module.exports = function() {
  var gulp = this;

  this.isWatching = false;

  this.setWatcher = function() {
    this.isWatching = true;
  };

  this.watcher = function() {
    if (this.isWatching) {
      return gulp.watch.apply(gulp, arguments);
    }
    return null;
  };

  this.pipeTimer = function(taskname) {
    taskname = taskname || '~~~';
    var startTime = new Date();

    return through(
      function() {
      },
      function() {
        if (gulp.isWatching) {
          this.on('end', function() {
            var time = new Date() - startTime;
            gutil.log('Watcher:',
              '\'' + gutil.colors.cyan(taskname) + '\'',
              're-bundle after',
              gutil.colors.magenta(time > 1000 ? time / 1000 + ' s' : time + ' ms'));
          });
        }
        this.queue(null);
      });
  };

  // --watch
  if (gutil.env.watch) {
    this.setWatcher();
  }

};