Node JS Object without name

Is there a way I can get array elements inside rooms array. There is an object without any name I guess and I am unable to parse through it.

rooms:
 { '':
    [ '1878016601075138296',
      '2087284131903222964',
      '435973380973917405' ] },
roomClients:
 { '1878016601075138296': { '': true },
   '2087284131903222964': { '': true },
   '435973380973917405': { '': true } }