角度 5 中加法两个数字的输出 NaN

Question

我正在尝试将两个数字相乘并添加另一个数字，但输出显示为 NaN。如何解决这个问题？

这是我的代码

medicines = [new Medicine()];
this.sum = 0;// sum also type of number
for (let i = 0; i < this.medicines.length; i++)
{
this.sum = this.sum + this.medicines[i].price * this.medicines[i].quantity;//here price and quantity of type number
console.log(typeof this.sum);//but this print NaN
}

药品模型

export class Medicine{
constructor(){}
name: String;
quantity:number;
price:number
}

Answer 1

它应该是这样的：

medicines:Medicine[]=[{name: 'name', quantity:3, price:6},{name: 'name', quantity:3, price:6},{name: 'name', quantity:3, price:6}]

或：

medicines: Array<Medicine> = new Array<Medicine>();

Answer 2

你能这样做吗

this.sum = this.sum + +this.medicines[i].price * +this.medicines[i].quantity;

将+放在属性之前，因此如果不是数字，它会将您的属性值转换为数字。

Answer 3

medicines: [] = new Medicine();
this.sum = 0;// sum also type of number
for (let i = 0; i < this.medicines.length; i++)
{
this.sum = this.sum + this.medicines[i].price * this.medicines[i].quantity;//here price and quantity of type number
console.log(typeof this.sum);//but this print NaN
}