accessing an object key name in an ionic view

I am trying to retrieve a userId which is stored in the key name of an object : {userID:{firstname:foo, lastname:bar}}

I am doing this from an ionic view :

<ion-item ng-repeat="x in people" class="item item-icon-right" 
ui-sref="app.people.profile({userId: x.howdoIextractmykeyname"})  >

I tried using this to extract the key name : Object.keys(myVar)[0]

ie:

<ion-item ng-repeat="x in people" class="item item-icon-right" 
ui-sref="app.people.profile({userId: Object.keys(x)[0]"})  >

but this does not seem to work

Any help appreciated!