ngx chart data with pipe

Question

I am using a filter pipe with the ngx-charts data array. The data is filtered by 2 dates: fromDate and toDate. The pipe is working fine when filtering with dates that make the array smaller, but when I filter first with a smaller date-range and then make the range bigger again, the pipe does not work with the original array but with the already filtered array.

I have already done other pips and never came across this problem, I am not sure what is going wrong here. Maybe someone of you can help me out.

pipe:

export class DateInRangePipe implements PipeTransform {
    transform(obj: any[], from: Date, to: Date): any[] {
        if (obj && from && to) {
            obj.forEach(data => {
                data.series = data.series.filter((item: any) => {
                    return this.inRange(item.name, from, to);
                });
            });
        }
        return [...obj];
    }

    inRange(date: Date, from: Date, to: Date): boolean {
        return date.getTime() >= from.getTime() &&
            date.getTime() <= to.getTime() ? true : false;
    }
}

Chart.component.html part

<ngx-charts-line-chart
    [view]="view"
    [scheme]="colorScheme"
    [results]="multi | dateinrangePipe: from: to"
    [gradient]="gradient"
    [xAxis]="showXAxis"
    [yAxis]="showYAxis"
    [legend]="showLegend"
    [showXAxisLabel]="showXAxisLabel"
    [showYAxisLabel]="showYAxisLabel"
    [xAxisLabel]="xAxisLabel"
    [yAxisLabel]="yAxisLabel"
    [autoScale]="autoScale"
    (select)="onSelect($event)">
</ngx-charts-line-chart>

Answer 1

`data.series = data.series.filter...` 

is a reference to the original object. To break the reference a clone of the obj Array has to be made at the beginning.