javascript - spread properties with multiple changes: one-liner ecma immutability -

i changed

const newcities = {...newstate.cities}; newcities[action.payload.id] = action.payload; newstate.cities = newcities; 

to one-liner

newstate.cities = {...newstate.cities, [action.payload.id]: action.payload}; 

but how change this

const newcities = {...newstate.cities}; action.payload.foreach(city=> newcities[city.id] = city); newstate.cities = newcities; 

to one-liner? ~=

newstate.cities = {...newstate.cities, action.payload.map(city=> [city.id]: city)}; 

final solution:

newstate.cities = {...newstate.cities, ...action.payload.reduce((o,a)=> ({...o,[a.id]:a}),{})}; 

previously forgot initialize reduce array =)

old approaches: may way?

newstate.cities = {...newstate.cities, ...action.payload.map(city=> ({[city.id]: city}) )}; 

updated:

newstate.cities = {...newstate.cities, ...action.payload.reduce(city=> ({[city.id]:city}) )}; 

update (complete ugliness):

newstate.cities = {...newstate.cities, ...action.payload.map((o)=> ({[o.id]:o}) ).reduce((o,a)=>({...o,...a}))};