Add Group By Pipe

src/app/pipes/array/groupBy.spec.ts

@@ -0,0 +1,61 @@
+import { GroupByPipe } from './groupBy';
+
+describe('Pipe: GroupBy', () => {
+  it('create an instance', () => {
+    let pipe = new GroupByPipe();
+    expect(pipe).toBeTruthy();
+  });
+
+});
+describe('GroupByPipe', () => {
+  let pipe: GroupByPipe;
+
+  beforeEach(() => {
+    pipe = new GroupByPipe();
+  });
+
+  it('should not change anything if not array', () => {
+    expect(pipe.transform('foo')).toEqual('foo');
+    expect(pipe.transform(null)).toEqual(null);
+    expect(pipe.transform(undefined)).toEqual(undefined);
+    expect(pipe.transform(42)).toEqual(42);
+    expect(pipe.transform({ foo: 1, bar: 2 })).toEqual({ foo: 1, bar: 2 });
+  });
+
+  it('group on discriminator', () => {
+    let arrayWithDiscriminator = [
+      {
+        key: 'value0'
+      },
+      {
+        key: 'value1'
+      },
+      {
+        key: 'value0'
+      },
+      {
+        key: 'value1'
+      }
+    ];
+    let result = pipe.transform(arrayWithDiscriminator, 'key');
+    expect(result).toEqual([ [ 'value0', [ { key: 'value0' }, { key: 'value0' }] ], [ 'value1', [ { key: 'value1' }, { key: 'value1' }] ] ]);
+  });
+  it('allow function to be used as discriminator', () => {
+    let arrayWithDiscriminator = [
+      {
+        key: 'value0'
+      },
+      {
+        key: 'value1'
+      },
+      {
+        key: 'value0'
+      },
+      {
+        key: 'value1'
+      }
+    ];
+    let result = pipe.transform(arrayWithDiscriminator, (instance: any) => { return instance[ 'key' ] });
+    expect(result).toEqual([ [ 'value0', [ { key: 'value0' }, { key: 'value0' }] ], [ 'value1', [ { key: 'value1' }, { key: 'value1' }] ] ]);
+  });
+});

src/app/pipes/array/groupBy.ts

@@ -0,0 +1,23 @@
+import { Pipe, PipeTransform } from '@angular/core';
+
+@Pipe({
+  name: 'groupBy'
+})
+export class GroupByPipe implements PipeTransform {
+  groupBy = (list: any[], discriminator: Function | string) => {
+    let map = list.reduce((acc, payload, i) => {
+      let key = discriminator instanceof Function ? discriminator(payload) : payload[ discriminator ];
+      return Object.assign({}, acc, {
+        [ key ]: acc[ key ] instanceof Array ? acc[ key ].concat([ payload ]) : [ payload ]
+      });
+    }, {});
+    return Object.keys(map).map((key: string) => [ key, map[ key ] ]);
+  }
+  transform(arr: any, ...args: any[]): any {
+    if (!Array.isArray(arr)) {
+      return arr;
+    }
+    return this.groupBy(arr, args[ 0 ]);
+  }
+
+}

src/app/pipes/array/index.ts

@@ -1,32 +1,33 @@
-import {DiffPipe} from './diff';
-import {InitialPipe} from './initial';
-import {FlattenPipe} from './flatten';
-import {IntersectionPipe} from './intersection';
-import {ReversePipe} from './reverse';
-import {TailPipe} from './tail';
-import {TrurthifyPipe} from './truthify';
-import {UnionPipe} from './union';
-import {UniquePipe} from './unique';
-import {WithoutPipe} from './without';
-import {PluckPipe} from './pluck';
-import {ShufflePipe} from './shuffle';
-import {EveryPipe} from './every';
-import {SomePipe} from './some';
-import {SamplePipe} from './sample';
-import {NgModule} from '@angular/core';
+import { DiffPipe } from './diff';
+import { InitialPipe } from './initial';
+import { FlattenPipe } from './flatten';
+import { IntersectionPipe } from './intersection';
+import { ReversePipe } from './reverse';
+import { TailPipe } from './tail';
+import { TrurthifyPipe } from './truthify';
+import { UnionPipe } from './union';
+import { UniquePipe } from './unique';
+import { WithoutPipe } from './without';
+import { PluckPipe } from './pluck';
+import { ShufflePipe } from './shuffle';
+import { EveryPipe } from './every';
+import { SomePipe } from './some';
+import { SamplePipe } from './sample';
+import { GroupByPipe } from './groupBy';
+import { NgModule } from '@angular/core';
 
 const ARRAY_PIPES = [
   DiffPipe, FlattenPipe, InitialPipe, IntersectionPipe, ReversePipe, TailPipe,
   TrurthifyPipe, UnionPipe, UniquePipe, WithoutPipe, PluckPipe, ShufflePipe,
-  EveryPipe, SomePipe, SamplePipe
+  EveryPipe, SomePipe, SamplePipe, GroupByPipe
 ];
 
 @NgModule({
-  declarations: [...ARRAY_PIPES],
+  declarations: [ ...ARRAY_PIPES ],
   imports: [],
-  exports: [...ARRAY_PIPES]
+  exports: [ ...ARRAY_PIPES ]
 })
-export class NgArrayPipesModule {}
+export class NgArrayPipesModule { }
 
 export * from './diff';
 export * from './initial';
@@ -43,3 +44,4 @@ export * from './shuffle';
 export * from './every';
 export * from './some';
 export * from './sample';
+export * from './groupBy';