如何从数组中嵌套具有重复值的对象

Question

I've got an array of objects for bus arrivals. The array has objects that have repeating properties but different times. I would like to nest the buses that come later into the bus that comes first. Also the array is ordered by arrival time.

[ 
   { Arrival, busId: "123", minToStop: 16, timeToStop: 957 },
   { Arrival, busId: "123", minToStop: 23, timeToStop: 1390 } 
]

Is there any nice and easy way to do it in javascript?

This is what I want to get

[ 
   { Arrival, busId: "123", minToStop: 16, timeToStop: 957, laterBuses: 
      [
         { Arrival, busId: "123", minToStop: 23, timeToStop: 1390 },
         { Arrival, busId: "123", minToStop: 30, timeToStop: 1820 }
      ]
   }
]

Answer 1

You can reduce the array to one value (a Map ) and then spread the values of that map as new array:

 const busses = [ { busId: '234', minToStop: 40, timeToStop: 1390 }, { busId: '123', minToStop: 16, timeToStop: 957 }, { busId: '123', minToStop: 23, timeToStop: 1490 }, { busId: '234', minToStop: 17, timeToStop: 957 }, { busId: '123', minToStop: 40, timeToStop: 1390 }, { busId: '123', minToStop: 30, timeToStop: 1390 }, { busId: '234', minToStop: 1, timeToStop: 1490 }, ]; console.log([ ...busses .sort((a, b) => a.minToStop - b.minToStop) .reduce((result, bus) => { const parentBus = result.get(bus.busId); const current = parentBus || { ...bus, laterBusses: [], }; if (!!parentBus) { //only add to laterbusses if it's not the first bus found current.laterBusses.push(bus); } return result.set(current.busId, current); }, new Map()) .values(), ]); 

Answer 2

This solution will first sort the buses by minToStop and then by busId . It then iterates through the buses array and conditionally puts the bus at the top level of a final array or nested as you requested.

 const buses = [ { busId: "234", minToStop: 40, timeToStop: 1390 }, { busId: "123", minToStop: 16, timeToStop: 957 }, { busId: "123", minToStop: 23, timeToStop: 1490 }, { busId: "234", minToStop: 17, timeToStop: 957 }, { busId: "123", minToStop: 30, timeToStop: 1390 }, { busId: "234", minToStop: 1, timeToStop: 1490 } ]; buses.sort((a,b) => a.minToStop - b.minToStop); buses.sort((a,b) => a.busId > b.busId); let formatted = []; buses.forEach(bus => { if ( formatted.length > 0 && formatted[formatted.length - 1].busId === bus.busId ) { formatted[formatted.length - 1].laterBuses.push(bus); } else { bus.laterBuses = []; formatted.push(bus); } }); console.log(formatted);