Setup selenium-webdriver with chrome options to change download directory.

test.js

var webdriver = require('selenium-webdriver'),
    chromeDriver = require('selenium-webdriver/chrome'),
    By = require('selenium-webdriver').By,
    until = require('selenium-webdriver').until;

var options = new chromeDriver.Options();
options.addArguments('start-maximized');
options.addArguments('incognito');
options.setUserPreferences({'download.default_directory' : '/path/to/your/download/directory'});

var driver = new webdriver.Builder()
    .withCapabilities(webdriver.Capabilities.chrome())
    .forBrowser('chrome')
    .setChromeOptions(options)
    .build();