How to give each element of an array of ojects a key

If I have an array that looks like:

arr =[ { id: ‘f794’,label: ‘Blue Bird’ } ]

how do I give the element of it a key so I get

arr =["myKey":{ id: 'f794',label: 'Blue Bird' } ]

I have tried several different ways, like

arr[0]= '"myKey"' + ":" + arr[0]

which gives me

[ "myKey:[object Object]" ]

How do I get arr =["myKey":{ id: 'f794',label: 'Blue Bird' } ]

Thanks