Node JS SDK V2, searchRecords using a custom field as a search parameter

Node JS SDK V2, searchRecords using a custom field as a search parameter

Hi! I'm making a Node.js app that connects with Zoho CRM with the ZohoCRM Node.js SDK Version 2. I need to search records from the CRM using a custom fields value as a parameter. I'm guessing this can be done but couldn't find any documentation on how to do it. 

So my question is: How to use custom field values as searchRecords()-parameter?