Aura:iteration is only for Arrays / list . If I have json or some kind of JS object to be iterated (like ng-repeat) how do I do it?
In your component's js controller, iterate through the properties and put them in an array.
Then use that array on aura:iteration.
I have an example here (github) that iterates all the fields on a generic sobject: https://github.com/mshanemc/soql2list/tree/master/src/aura/AllFieldDisplayer