React/JSX/ES6 setup.

.eslintrc

{
  "ecmaFeatures": {
    "arrowFunctions": true,
    "blockBindings": false,
    "classes": true,
    "forOf": true,
    "jsx": true,
    "modules": true,
    "objectLiteralShorthandMethods": true
  },

  "env": {
    "browser": true,
    "node": true
  },

  "plugins": [
    "react"
  ],

  "rules": {
    "react/jsx-uses-vars": 1,
    "no-underscore-dangle": 0
  }
}

Gruntfile

module.exports = function (grunt) {
  grunt.loadNpmTasks('grunt-contrib-watch');
  grunt.loadNpmTasks('grunt-eslint');
  grunt.loadNpmTasks('grunt-browserify');

  grunt.initConfig({
    browserify: {
      dist: {
        files: {
          'bundle.js': ['src/app.js']
        },
        options: {
          transform: [['babelify', { optional: ['runtime'] }]],
          browserifyOptions: {
            debug: true
          }
        }
      }
    },
    eslint : {
      target: ["src/**/*.js"]
    },
    watch: {
      scripts: {
        files: ['src/**/*.js'],
        tasks: ['eslint', 'browserify'],
        options: {
          atBegin: true,
          spawn: true
        }
      }
    }
  });

  grunt.registerTask("default", ["watch"]);
}

package.json

{
  "name": "project",
  "version": "1.0.0",
  "description": "Put in description here",
  "author": "<Your name>",
  "devDependencies": {
    "babel": "^5.8.12",
    "babel-runtime": "^5.8.12",
    "babelify": "^6.1.3",
    "eslint": "^0.24.1",
    "expect.js": "^0.3.1",
    "grunt": "^0.4.5",
    "grunt-browserify": "^3.8.0",
    "grunt-contrib-watch": "^0.6.1",
    "grunt-eslint": "^16.0.0",
    "mocha": "^2.2.5"
  },
  "dependencies": {
    "eslint-plugin-react": "^2.7.1",
    "react": "^0.13.3",
    "reflux": "^0.2.10"
  },
  "scripts": {
    "specs": "mocha --ui tdd --compilers js:babel/register spec/**/*"
  }
}