How do you read a cookie in Express.js?

Read an incoming cookie via req.cookies.keyName on the request object.

function (req, res) {
  if ('lastUsedName' in req.cookies &&
      req.cookies.lastUsedName !== '') {
    let value = req.cookies.lastUsedName;
    // use the value
  }
}

Important: Always validate cookie values - check existence and content, just like query parameters or request body. Users can modify cookies in their browser.