如何在Javascript中设置不可变状态的值？
如何在Javascript中设置不可变状态的值？
提问于 2018-06-08 05:22:37
给定一个不可变状态，如下所示：
alerts: {
5a8c76171bbb57b2950000c4: [
{
_id:5af7c8652552070000000064
device_id:5a8c76171bbb57b2950000c4
count: 1
},
{
_id:5af7c8722552070000000068
device_id:5a8c76171bbb57b2950000c4
count: 2
}
]
}和一个像这样的对象：
{
_id:5af7c8652552070000000064
device_id:5a8c76171bbb57b2950000c4
count: 2
}我想在警报状态(不可变)中用相同的id替换对象，这样最终结果如下所示：
alerts: {
5a12356ws13tch: [
{
_id:5af7c8652552070000000064
device_id:5a8c76171bbb57b2950000c4
count: 2
},
{
_id:5af7c8722552070000000068
device_id:5a8c76171bbb57b2950000c4
count: 2
}
]
}我该怎么做呢？在列表、地图或OrderedMap上找到mergeDeep、getIn、setIn和updateIn？
我试着做这样的事情..其中index为0，deviceId为5a12356ws13tch
但是不起作用。
export const oneAlertFetched = (state, {deviceId, index, alert}) => state.setIn(['alerts', deviceId, index], alert).merge({fetching: false})我也试过了。不起作用。
export const oneAlertFetched = (state, {deviceId, index, alert}) => {
const a = state.alerts[deviceId][index]
state.alerts[deviceId][index] = Object.assign({}, a, alert)
return
}回答 1
Stack Overflow用户
回答已采纳
发布于 2018-06-08 06:23:49
我想你的意思是你想用更新后的负载返回一个新的对象？
function getNextAlerts(alerts, parentDeviceId, payload) {
const alertsForDevice = alerts[parentDeviceId];
if (!alertsForDevice || alertsForDevice.length === 0) {
console.log('No alerts for device', deviceId);
return;
}
return {
...alerts,
[parentDeviceId]: alerts[parentDeviceId].map(item =>
item._id === payload._id ? payload : item
),
}
}
const alerts = {
'5a12356ws13tch': [
{
_id: '5af7c8652552070000000064',
device_id: '5a8c76171bbb57b2950000c4',
count: 1
},
{
_id: '5af7c8722552070000000068',
device_id: '5a8c76171bbb57b2950000c4',
count: 2
}
]
};
const nextAlerts = getNextAlerts(alerts, '5a12356ws13tch', {
_id: '5af7c8652552070000000064',
device_id: '5a8c76171bbb57b2950000c4',
count: 2,
});
console.log('nextAlerts:', nextAlerts);<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.10/lodash.min.js"></script>
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原文链接：
https://stackoverflow.com/questions/50750350
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