Javascript 添加数字并得到错误的输出

currentValue为0，selection为3或8，nextValue为23 当得到结果而不是总的附加值时，它变成了0323，而不是23+3，即26

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基本问题是JS将“选择”识别为字符串，而不是数值。所以它是“连接”，而不是“添加”。

可能

选择

是字符串，它使所有方程都变成字符串。因此0+'3'+23=0323。使用

Number（shipping.overseas）

或

+shipping.overseas

使其成为实数

const [shipping, setShipping] = useState({
        overseas: '3'
});

const handleChange = (e) => {
    setShipping({ overseas: e.target.value});  //can change to 8 or 3
};
const selection = parseInt(shipping.overseas);

console.log(selection);   // result from selection are correct

const getTotal = () => {
    return products.reduce((currentValue, nextValue) => {
        return  (currentValue + selection + nextValue.count * nextValue.price);
    }, 0);
};

或

---

const selection=parseInt（shipping.overseas）

shipping.overseas是一个字符串，因此需要将其强制转换为int

const [shipping, setShipping] = useState({
        overseas: '3'
});

const handleChange = (e) => {
    setShipping({ overseas: e.target.value});  //can change to 8 or 3
};
const selection = parseInt(shipping.overseas);

console.log(selection);   // result from selection are correct

const getTotal = () => {
    return products.reduce((currentValue, nextValue) => {
        return  (currentValue + selection + nextValue.count * nextValue.price);
    }, 0);
};

const selection = parseInt(shipping.overseas);

const selection =+shipping.overseas