how to select a dropdown value in selenium webdriver using node.js

You can create a function that select the value you desire

like this...

driver.wait(
    until.elementLocated(By.id("continents")), 20000
).then(element => {
    selectByVisibleText(element, "Africa")
});

function selectByVisibleText(select, textDesired) {
    select.findElements(By.tagName('option'))
    .then(options => {
        options.map(option => {
            option.getText().then(text => {
                if (text == textDesired)
                    option.click();
            });
        });
    });
}

Just click the desired option.

driver.findElement(webdriver.By.css('#mySelection > option:nth-child(4)'))
    .click();

or by value

driver.findElement(webdriver.By.css('#mySelection > option[value=apple]'))
    .click();

Note that I've changed your 'By' to a css selector. I'm lazy and like to just drill into the option from developer tools and select Copy CSS Path (chrome) or Copy Unique Selector (firefox).

For anyone stuck on this, here is how I did it for a <select> option:

<select id='mySelection'>
   <option value='0'>Hello</option>
   <option value='1'>Everybody</option>
   <option value='2'>Got</option>
   <option value='3'>It</option>
</select>

In Selenium for NodeJS, you would grab the It <option>:

var webdriver = require('selenium-webdriver');

var driver = new webdriver.Builder().
   withCapabilities(webdriver.Capabilities.chrome()).
   build();


driver.findElement(webdriver.By.id('mySelection')).sendKeys('It');

When you .sendKeys() for the option it has to equal the text displayed to the user in the dropdown.

In your case just grab the parent element then sendKeys() for the child element.