Uglify size comparison between mangled and non-mangled variable names (using Bootstrap as example)

Gruntfile.js

module.exports = function(grunt) {

  grunt.loadNpmTasks('grunt-contrib-uglify');
  
  var files = [ grunt.option('js') || 'node_modules/bootstrap/js/*.js' ];

  grunt.initConfig({
    uglify: {
      options: {
        report: 'gzip'
      },
      mangle: {
        files: {
          'dist/mangle.js': files
        }
      },
      no_mangle: {
        options: {
          mangle: false
        },
        files: {
          'dist/no_mangle.js': files
        }
      }
    }
  });
  
  grunt.registerTask('default', ['uglify:mangle', 'uglify:no_mangle']);

  // $ grunt --no-color > output.txt
  // $ grunt --no-color --js "some/other/js/**/*.js" > output.txt

}

output.txt

Running "uglify:mangle" (uglify) task
File dist/mangle.js created: 54.98 kB → 28.85 kB → 5.09 kB (gzip)

Running "uglify:no_mangle" (uglify) task
File dist/no_mangle.js created: 54.98 kB → 35.15 kB → 5.94 kB (gzip)

Done, without errors.

package.json

{
  "name": "uglify-test",
  "version": "0.0.0",
  "description": "",
  "main": "Gruntfile.js",
  "dependencies": {
    "grunt": "~0.4.5",
    "grunt-contrib-uglify": "~0.4.0"
  },
  "devDependencies": {},
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC"
}