switchtask.js

// Run with: grunt switchwatch:target1:target2 to only watch those targets
grunt.registerTask('switchwatch', function() {
  var targets = Array.prototype.slice.call(arguments, 0);
  Object.keys(grunt.config('watch')).filter(function(target) {
    return !(grunt.util._.indexOf(targets, target) !== -1);
  }).forEach(function(target) {
    grunt.log.writeln('Ignoring ' + target + '...');
    grunt.config(['watch', target], {files: []});
  });
  grunt.task.run('watch');
});