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¿Cómo agrupar datos en Angular 2?

Question

¿Cómo puedo agrupar datos en Angular 2 con TypeScript? Soy consciente de que esto se hace usando el filtro "agrupar por" en Angular 1.X, pero no obteniendo cómo agrupar datos en Angular 2. Tengo esta matriz:

import {Employee} from ''./employee'';
        export var employees: Employee[];
        employees = [
            { id: 1, firstName: "John", lastName: "Sonmez", department: 1, age: 24, address: "24/7, Working hours apartment, Cal. US", contactNumber: "[phone]" },
            { id: 2, firstName: "Mark", lastName: "Seaman", department: 2, age: 25, address: "32-C, Happy apartments, Block-9C, Cal. US", contactNumber: "[phone]" },
            { id: 3, firstName: "Jamie", lastName: "King", department: 3, age: 32, address: "54/II, Glorydale apartment, Cal. US", contactNumber: "[phone]" },

            { id: 5, firstName: "Jacob", lastName: "Ridley", department: 5, age: 24, address: "24/7, Working hours apartment, Cal. US", contactNumber: "[phone]" },
            { id: 6, firstName: "Peter", lastName: "Parker", department: 3, age: 25, address: "32-C, Happy apartments, Block-9C, Cal. US", contactNumber: "[phone]" },
            { id: 7, firstName: "Martin", lastName: "Luther", department: 4, age: 32, address: "54/II, Glorydale apartment, Cal. US", contactNumber: "[phone]" },
            { id: 8, firstName: "Raghav", lastName: "Kumar", department: 1, age: 34, address: "51/C Shivalik, Cal. US", contactNumber: "[phone]" },

            { id: 9, firstName: "Narayan", lastName: "Sonmez", department: 3, age: 24, address: "24/7, Working hours apartment, Cal. US", contactNumber: "[phone]" },
            { id: 10, firstName: "Russell", lastName: "Andre", department: 2, age: 25, address: "32-C, Happy apartments, Block-9C, Cal. US", contactNumber: "[phone]" },
            { id: 11, firstName: "Ramona", lastName: "King", department: 4, age: 32, address: "54/II, Glorydale apartment, Cal. US", contactNumber: "[phone]" },
            { id: 12, firstName: "Andre", lastName: "Russell", department: 1, age: 34, address: "51/C Shivalik, Cal. US", contactNumber: "[phone]" },

            { id: 13, firstName: "Nathan", lastName: "Leon", department: 1, age: 24, address: "24/7, Working hours apartment, Cal. US", contactNumber: "[phone]" },
            { id: 14, firstName: "Brett", lastName: "Lee", department: 5, age: 25, address: "32-C, Happy apartments, Block-9C, Cal. US", contactNumber: "[phone]" },
            { id: 15, firstName: "Tim", lastName: "Cook", department: 2, age: 32, address: "54/II, Glorydale apartment, Cal. US", contactNumber: "[phone]" },
            { id: 16, firstName: "Steve", lastName: "Jobs", department: 5, age: 34, address: "51/C Shivalik, Cal. US", contactNumber: "[phone]" }
        ];

y estoy buscando contar a los empleados por departamento, como

El departamento 1 tiene 4 empleados

y así.

Unir la identificación del departamento con el departamento real (para poder obtener el nombre del departamento) es otra historia que necesito descubrir.

Answer 1

Puede usar una tubería personalizada para hacerlo como se describe a continuación:

@Pipe({name: ''groupBy''})
export class GroupByPipe implements PipeTransform {
  transform(value: Array<any>, field: string): Array<any> {
    const groupedObj = value.reduce((prev, cur)=> {
      if(!prev[cur[field]]) {
        prev[cur[field]] = [cur];
      } else {
        prev[cur[field]].push(cur);
      }
      return prev;
    }, {});
    return Object.keys(groupedObj).map(key => ({ key, value: groupedObj[key] }));
  }
}

Y luego en tu plantilla puedes escribir:

<div *ngFor="let item of employees | groupBy:''department''">
  Department {{ item.key }} has {{ item.value.length }} employees
</div>

Consulte también el plunker correspondiente https://plnkr.co/edit/cLnlH13IH4WAsuRdol4n?p=preview

Espero que te ayude!

Answer 2

Puede usar ngx-pipes https://github.com/danrevah/ngx-pipes#groupby

this.arrayObject = [
  {id: 1, elm: ''foo'', value: 0}, 
  {id: 2, elm: ''bar'', value: 1}, 
  {id: 3, elm: ''foo'', value: 2}, 
  {id: 4, elm: ''foo'', value: 2}
];

this.arrayNestedObject = [
  {id: 1, prop: { deep: ''foo'' }},
  {id: 2, prop: { deep: ''bar'' }},
  {id: 3, prop: { deep: ''foo'' }},
  {id: 4, prop: { deep: ''bar'' }}
];

<p>{{ arrayObject | groupBy: ''elm'' }}</p> 
<!-- Output: "{foo: [{id: 1, elm: ''foo'', value: 0}, {id: 3, elm: ''foo'', value: 2}, {id: 4, elm: ''foo'', value: 2}], bar: [{id: 2, elm: ''bar'', value: 1}]}" -->

Answer 3

var dept = employees.map((m) => m.department).filter((f, i, ar) => ar.indexOf(f) === i);
console.log(dept);

var group = employees.reduce((accumulator, item, i, arr) => {
  if (dept.length) {
    var pop = dept.shift();
    var list = arr.filter((f) => f.department == pop);
    accumulator.push(...list);
  }
  return accumulator;
}, []);

console.log(group);