Calling an value in an array with a variable

I have the following link to an array object:
itemData . lyra [ 0 ]. stunden

How can I replace lyra (one of 10 devices) with a variable?
let device = lyra
itemData . device [ 0 ]. stunden OR
itemData . + device + [ 0 ]. stunden
Thanks for your help!

J Florian

Problem SOLVED:
itemData[ device] [ 0 ]. stunden