将数组中的项相乘并找到数组中所有行的相乘结果的总和

每当我单击下面的按钮时，它都会调用 populateGridWithSelectedData 方法。

    <Button variant="contained" color="primary" onClick= {this.populateGridWithSelectedData} >ADD</Button>


    populateGridWithSelectedData(){         

            let items = [...this.state.items];
            items.push({
                invoiceLine: this.state.concatenatedInvoiceLine,
                settledQuantity: this.state.settledQuantity,
                price: this.state.unitPrice,
                creditedQuantity: this.state.creditedQuantity,
                reasonCode: this.state.reasonCode
            });

            this.setState({
                items,
                invoiceLine: '',
                settledQuantity:'',
                price:'',
                creditedQuantity:'',
                reasonCode:''
            });                        
        }

我正在将数据推送到数组中。这可能是大量数据。我希望能够在每次推送时执行以下操作

1. 乘以价格和信用数量。将该行的结果存储在某处，对添加的所有行执行相同的操作，并在一天结束时找到所有行的乘法总数。

这似乎不起作用。

    var total = 0;
    var multipliedResult = 0;

    for (var x in items){
        multipliedResult = (price * creditedQuantity);
        total = (total + multipliedResult);
    } 

我究竟做错了什么？