export class TableSortDemo implements OnInit {

    cars1: Car[];

    cars2: Car[];

    cars3: Car[];

    cols: any[];

    constructor(private carService: CarService) { }

    ngOnInit() {
        this.carService.getCarsSmall().then(cars => this.cars1 = cars);
        this.carService.getCarsSmall().then(cars => this.cars2 = cars);
        this.carService.getCarsSmall().then(cars => this.cars3 = cars);

        this.cols = [
            { field: 'vin', header: 'Vin' },
            { field: 'year', header: 'Year' },
            { field: 'brand', header: 'Brand' },
            { field: 'color', header: 'Color' }
        ];
    }

    customSort(event: SortEvent) {
        event.data.sort((data1, data2) => {
            let value1 = data1[event.field];
            let value2 = data2[event.field];
            let result = null;

            if (value1 == null && value2 != null)
                result = -1;
            else if (value1 != null && value2 == null)
                result = 1;
            else if (value1 == null && value2 == null)
                result = 0;
            else if (typeof value1 === 'string' && typeof value2 === 'string')
                result = value1.localeCompare(value2);
            else
                result = (value1 < value2) ? -1 : (value1 > value2) ? 1 : 0;

            return (event.order * result);
        });
    }
}

<h3 class="first">Single Sort</h3>
<p-table [columns]="cols" [value]="cars1">
    <ng-template pTemplate="header" let-columns>
        <tr>
            <th *ngFor="let col of columns" [pSortableColumn]="col.field">
                {{col.header}}
                <p-sortIcon [field]="col.field"></p-sortIcon>
            </th>
        </tr>
    </ng-template>
    <ng-template pTemplate="body" let-rowData let-columns="columns">
        <tr>
            <td *ngFor="let col of columns">
                {{rowData[col.field]}}
            </td>
        </tr>
    </ng-template>
</p-table>

<h3>Multi Sort with MetaKey</h3>
<p-table [columns]="cols" [value]="cars2" sortMode="multiple">
    <ng-template pTemplate="header" let-columns>
        <tr>
            <th *ngFor="let col of columns" [pSortableColumn]="col.field">
                {{col.header}}
                <p-sortIcon [field]="col.field"></p-sortIcon>
            </th>
        </tr>
    </ng-template>
    <ng-template pTemplate="body" let-rowData let-columns="columns">
        <tr>
            <td *ngFor="let col of columns">
                {{rowData[col.field]}}
            </td>
        </tr>
    </ng-template>
</p-table>

<h3>Custom Sort</h3>
<p-table [columns]="cols" [value]="cars3" (sortFunction)="customSort($event)" [customSort]="true">
    <ng-template pTemplate="header" let-columns>
        <tr>
            <th *ngFor="let col of columns" [pSortableColumn]="col.field">
                {{col.header}}
                <p-sortIcon [field]="col.field"></p-sortIcon>
            </th>
        </tr>
    </ng-template>
    <ng-template pTemplate="body" let-rowData let-columns="columns">
        <tr>
            <td *ngFor="let col of columns">
                {{rowData[col.field]}}
            </td>
        </tr>
    </ng-template>
</p-table>