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[英]How to update a useState which has an array, inside this array I have objects this objects will update when the input value will change in react js
[英]How to update array of objects in react native useState inside for loop?
我有一个包含对象数组的 state,我想在 for 循环中更新我的 object。 这是我的代码:每个对象都包含值、文本和时间。 时间应该在 for 循环内更新。
const [initialValues, setInitialValue] = useState([
{
value: 128,
text: '128 Kb',
time: ''
},
{
value: 256,
text: '256 Kb',
time: ''
},
{
value: 512,
text: '512 Kb',
time: ''
},
{
value: 750,
text: '750 Kb',
time: ''
},
{
value: 1024,
text: '1 MB',
time: ''
},
{
value: 2048,
text: '2 MB',
time: ''
},
{
value: 3072,
text: '3 MB',
time: ''
},
{
value: 4096,
text: '4 MB',
time: ''
},
{
value: 5120,
text: '5 MB',
time: ''
}
]);
我想更新我的 state 的 for 循环:计算是一个 function,它将在用户端的onPress事件上被调用。
const [number, setNumber] = useState('1')
const [data, setData] = useState('1024')
const calculate = () => {
if (number) {
let size = number * data * 8
size = percentage(12, size) + size;
for (let value of initialValues) {
let data = value.value;
data = (size / data).toFixed();
// here is my approach but not correct
setInitialValue({ ...initialValues, time: data })
}
}
}
但结果是不确定的。
你应该改变你的计算 function 到这个
const calculate = () => {
if (number) {
let size = number * data * 8;
size = percentage(12, size) + size;
const newValues = [...initialValues.slice()];
for (let i = 0; i < newValues.length; i++) {
let data = (size / data).toFixed();
newValues[i].time = data;
}
setInitialValue(newValues);
}
}
将初始值存储在变量中并像这样将其传递给 useState
const [initialValues, setInitialValue] = useState(initialVaule);
const [number, setNumber] = useState(1)
const [data, setData] = useState(1024)
const calculate = () => {
if (number && data) {
let size = number * data * 8
size = percentage(12, size) + size;
let updatedValue = intialValues.map( item => {
return item.time = (size / data).toFixed();
})
setInitialValue(updatedValue);
}
}
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