Improve sort pipe to take multiple args

dashboard/src/app/artist.component.html

@@ -1,7 +1,7 @@
 <h1>{{albumName}}</h1>
 
 <ul class="heroes">
-    <li *ngFor="let song of songs | sortBy : 'Track Number'" >
+    <li *ngFor="let song of songs | sortBy : 'Album':'Track Number'" >
         {{("0" + song['Track Number']).slice(-2)}}. {{song.Name}} -- {{song.Artist}} -- {{song.Album}}
     </li>
 </ul>

dashboard/src/app/sortby.pipe.ts

@@ -1,28 +1,23 @@
-// Thank to http://4dev.tech/2016/09/angular2-how-to-sort-a-json-dataset-by-field/
+// Thank to http://4dev.tech/2016/09/angular2-how-to-sort-a-json-dataset-by-field/ for the pipe
+// Thank to http://stackoverflow.com/questions/28560801/javascript-sorting-array-by-multiple-criteria for the multi-args part
 
 import { Pipe, PipeTransform } from '@angular/core';
 
 @Pipe({name: "sortBy"})
 export class SortPipe implements PipeTransform {
-  transform(array: Array<string>, args: string): Array<string> {
+  transform(array: Array<string>, ...args: any[]): Array<string> {
+		console.log("test: " + args);
 		array.sort((a: any, b: any) => {
-			if (a[args] == undefined && b[args] == undefined) {
+			for (let i = 0; i < array.length; i++) {
-				return 0;
+				let arg = args[i];
-			}
-			if (a[args] == undefined && b[args] != undefined) {
-				return -1;
-			}
-			if (a[args] != undefined && b[args] == undefined) {
-				return 1;
-			}
 
-	    if ( a[args] < b[args] ){
+				if (a[arg] == undefined && b[arg] != undefined) return -1;
-	    	return -1;
+				if (a[arg] != undefined && b[arg] == undefined) return 1;
-	    }else if( a[args] > b[args] ){
+
-				return 1;
+				if (a[arg] < b[arg]) return -1;
-	    }else{
+				if (a[arg] > b[arg]) return 1;
-	    	return 0;
 			}
+			return 0;
 		});
     return array;
   }