Comment grouper des données dans Angular 2 ?

Question

Comment regrouper des données dans Angular 2 avec TypeScript. Je sais que cela se fait en utilisant le filtre "group by" dans Angular 1.X, mais je ne comprends pas comment grouper des données dans Angular 2. J'ai ce tableau :

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: "+968546215789" },
            { id: 2, firstName: "Mark", lastName: "Seaman", department: 2, age: 25, address: "32-C, Happy apartments, Block-9C, Cal. US", contactNumber: "+968754216984" },
            { id: 3, firstName: "Jamie", lastName: "King", department: 3, age: 32, address: "54/II, Glorydale apartment, Cal. US", contactNumber: "+967421896326" },

            { id: 5, firstName: "Jacob", lastName: "Ridley", department: 5, age: 24, address: "24/7, Working hours apartment, Cal. US", contactNumber: "+968546215789" },
            { id: 6, firstName: "Peter", lastName: "Parker", department: 3, age: 25, address: "32-C, Happy apartments, Block-9C, Cal. US", contactNumber: "+968754216984" },
            { id: 7, firstName: "Martin", lastName: "Luther", department: 4, age: 32, address: "54/II, Glorydale apartment, Cal. US", contactNumber: "+967421896326" },
            { id: 8, firstName: "Raghav", lastName: "Kumar", department: 1, age: 34, address: "51/C Shivalik, Cal. US", contactNumber: "+967842569842" },

            { id: 9, firstName: "Narayan", lastName: "Sonmez", department: 3, age: 24, address: "24/7, Working hours apartment, Cal. US", contactNumber: "+968546215789" },
            { id: 10, firstName: "Russell", lastName: "Andre", department: 2, age: 25, address: "32-C, Happy apartments, Block-9C, Cal. US", contactNumber: "+968754216984" },
            { id: 11, firstName: "Ramona", lastName: "King", department: 4, age: 32, address: "54/II, Glorydale apartment, Cal. US", contactNumber: "+967421896326" },
            { id: 12, firstName: "Andre", lastName: "Russell", department: 1, age: 34, address: "51/C Shivalik, Cal. US", contactNumber: "+967842569842" },

            { id: 13, firstName: "Nathan", lastName: "Leon", department: 1, age: 24, address: "24/7, Working hours apartment, Cal. US", contactNumber: "+968546215789" },
            { id: 14, firstName: "Brett", lastName: "Lee", department: 5, age: 25, address: "32-C, Happy apartments, Block-9C, Cal. US", contactNumber: "+968754216984" },
            { id: 15, firstName: "Tim", lastName: "Cook", department: 2, age: 32, address: "54/II, Glorydale apartment, Cal. US", contactNumber: "+967421896326" },
            { id: 16, firstName: "Steve", lastName: "Jobs", department: 5, age: 34, address: "51/C Shivalik, Cal. US", contactNumber: "+967842569842" }
        ];

et je cherche à compter les employés par département, par exemple

Le département 1 compte 4 employés

et ainsi de suite.

La jonction de l'identifiant du département avec le département réel (afin de pouvoir obtenir le nom du département) est une autre histoire que je dois résoudre.

Answer 1

Vous pouvez utiliser tuyau personnalisé pour le faire, comme décrit ci-dessous :

@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] }));
  }
}

Et ensuite, sur votre modèle, vous pouvez écrire :

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

Voir aussi le plunker correspondant https://plnkr.co/edit/cLnlH13IH4WAsuRdol4n?p=preview

J'espère que cela vous aidera !

Answer 2

Vous pouvez utiliser les 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);