How do I get confirmation that the piece of code completed its execution in Node.js

I am using array-query npm plugin and I have large array records from which I choose the records with matching conditions.

The code for it is as below.

code

var result = query(col).within(list).on(postDetails);

It will select records based on provided condition from postDetails array

Now how I can confirm that all matching records are selected before any other code executes as postDetails array is large and can take few time to complete.

via Chintanr