title: how to set cucumber environment variables
body: <p>I am having the following package.json:</p>
  
  <pre><code>{
    "name": "newcucumber",
    "version": "1.0.0",
    "main": "index.js",
    "scripts": {
      "test": "./node_modules/.bin/cucumber-js",
      "firefox": "./node_modules/.bin/cucumber-js -- --profile.desktop.env.browser ff"
    },
    "author": "",
    "license": "ISC",
    "dependencies": {
      "chromedriver": "^2.24.1",
      "cucumber": "^1.3.0",
      "firefox-profile": "^0.4.2",
      "geckodriver": "^1.1.2",
      "phantomjs-prebuilt": "^2.1.12",
      "selenium-webdriver": "^3.0.0-beta-2"
    }
  }
  </code></pre>
  
  <p>I run the program using:</p>
  
  <pre><code>npm test
  </code></pre>
  
  <p>I would like to set an environment variable for cucumber, such that I could run from the command line: <code>npm test firefox</code> or <code>npm test phantomjs</code>.</p>
  
  <p>It could also be as a part of package.json 'scripts' as seen above, but I am not sure if I did it right. Invoking <code>npm run-script firefox</code></p>
  
  <p>How does one implement it, such that in the js code, like world.js or browser.js I grab the env variable?</p>