我想在我的表中总结这些数字：

的数据
我需要做一个过滤器还是需要ngFor？我知道计算没有意义。我试探着：

<th>
    <i>Sum:{{ this.invoices?.sum | number }}</i>
 </th>

字符串
ts：

invoices: any;

  calcSum = ( invoice: any, sum:number): string => {
        if (!invoice||!sum) { 
            return '0';
        }
        return (this.invoices.sum + this.invoices.sum); 
        
    }

型
接口：

export interface InvoiceResponse{
    paid: boolean,
    paidAmount: number,
    client: string,
    number: number,
    total:number,
    taxTotal: number,
    sum: number,
    currencyRate: string,
    currencyRateAtIssueDate: string,
    issuedAtPlace: string,
    issuedAt: string,
    deadlineAt: string

型
}