Aquí hay una forma en que puede lograr esto usando reduce()

 let tasks = [{ id: 1, title: "call Tom", reminders: { date: "2022-02-01", time: "09:30" } }, { id: 2, title: "Meet Bred", reminders: { date: "2022-02-01", time: "10:30" } }, { id: 3, title: "Mail Susan", reminders: { date: "2022-03-01", time: "19:00" } }]; let combinedTasks = tasks.reduce((combined, x) => { // Try to find an existing item in the combined tasks array where the date equals this task item. let match = combined.find(y => y.reminders.date == x.reminders.date); if (match) { // If we find a match, add this task item's title to the combined item's tasks array. match.tasks.push(x.title); } else { // If we didn't find a match, take this task item and turn it into a combined tasks item with a tasks array so that future items in the tasks array can be combined with this one. let copy = { ...x }; copy.tasks = [x.title]; delete copy.title; combined.push(copy); } return combined; }, []); console.log(combinedTasks);

const tasks = [ { id: 1, title: "call Tom", reminders: { date: "2022-02-01", time: "09:30" } }, { id: 2, title: "Meet Bred", reminders: { date: "2022-02-01", time: "10:30" } }, { id: 3, title: "Mail Susan", reminders: { date: "2022-03-01", time: "19:00" } } ] tasks.sort((a,b)=>{ return new Date(a.reminders.date) - new Date(b.reminders.date) }) let output = []; tasks.map((val,index)=>{ if(index===0){ let obj = {} temp = []; temp.push(val.title); obj.id = val.id; obj.tasks = [...temp]; obj.reminders = {...val.reminders}; output.push(obj); }else{ if(output[output.length-1].reminders.date===val.reminders.date){ output[output.length-1].tasks.push(val.title); }else{ let obj = {} temp = []; temp.push(val.title); obj.id = val.id; obj.tasks = [...temp]; obj.reminders = val.reminders; output.push(obj); } } })

Pruebe esta solución, funciona.

 Output : [ { id: 1, tasks: [ 'call Tom', 'Meet Bred' ], reminders: { date: '2022-02-01', time: '09:30' } }, { id: 3, tasks: [ 'Mail Susan' ], reminders: { date: '2022-03-01', time: '19:00' } } ]

La salida de este código es la esperada. Espero que esto sea útil .

tienes razón, tienes que usar el método de reduce .

Úselo para recorrer su matriz inicial. Entonces, para cada tarea, puede ver en su matriz futura si tiene una tarea en la fecha de la tarea actual. De lo contrario, puede crear una nueva tarea y agregar las siguientes tareas más tarde.

 const tasks = [ { id: 1, title: "call Tom", reminders: { date: "2022-02-01", time: "09:30" } }, { id: 2, title: "Meet Bred", reminders: { date: "2022-02-01", time: "10:30" } }, { id: 3, title: "Mail Susan", reminders: { date: "2022-03-01", time: "19:00" } } ]; const combinatedTasks = tasks.reduce((_combinatedTasks, currentTask) => { const currentDate = currentTask.reminders.date; const combinatedTaskAtCurrentDate = _combinatedTasks.find(task => task.reminders.date === currentDate); if (combinatedTaskAtCurrentDate) { combinatedTaskAtCurrentDate.tasks.push(currentTask.title); } else { _combinatedTasks.push({ id: currentTask.id, tasks: [currentTask.title], reminders: currentTask.reminders }); } return _combinatedTasks; }, []); console.log(combinatedTasks);