WebdriverJS is another name for selenium-webdriver, the official Node.JS implementation of the JSONWire (WebDriver Wire) Protocol by the Selenium team.

WebdriverIO is an independent implementation of the JSON Wire Protocol by Christian Bromann (SO profile), who works at Sauce Labs, a provider of cloud-base cross-browser testing. WebdriverIO wraps its lower level requests into useful commands, with a concise syntax:

client

    .url('http://google.com')

    .setValue('#q','webdriver')

    .click('#btnG')

The same test with selenium-webdriver is more complicated:

driver.get('http://www.google.com');

driver.findElement(webdriver.By.id('q')).sendKeys('webdriver');

driver.findElement(webdriver.By.id('btnG')).click();

There are at least seven Webdriver clients written in Node.JS.