I need to process files in a specific order (Javascript)

I have 3 files. Their respective filename are:

1. OATH
2. PRVA
3. CONS

I need to process PRVA and CONS before processing OATH. How can I do this in Javascript?

Something like

if (filename.contains('PRVA')) {
        // do this
} else if (filename.contains('CONS')) {
        // do this
} else if, there is no more PRVA and CONS then do OATH