Question

我有一个示例，在该示例中，我需要根据星期几和选定的小时数存储几个价格。此数据作为对象出现，需要作为Map（）发送，因此后端可以使用它。不幸的是，它变成了一个对象。我认为它是在const price内部发生的，但是我需要一个更好的解决方案，所以它永远不会发生。我该如何实现？

componentDidMount = async () => {
const dataFromDb = data.get('getting data here')
console.log('dataFromDb' ,dataFromDb) // Data from DB

let reservationPrice = new Map(); 
console.log('reservationPrice a Map()?', reservationPrice) // a Map();

console.log("Am I an object", dataFromDb.reservationPrice) // Object from DB

if (Object.entries(dataFromDb.reservationPrice).length === 0) {
console.log('entered') // not entering here

let maxHour = moment().startOf('day') // 00:00:00
let minHour = maxHour.clone().endOf('day') // 23:59:59

Object.keys(dataFromDb.schedule).map(key => { //getting schedule from DB
  if (dataFromDb.operationSchedule[key] && moment(dataFromDb.operationSchedule[key].startTime, 'HH:mm') < minHour) {
    minHour = moment(dataFromDb.operationSchedule[key].startTime, 'HH:mm')
  }
  if (dataFromDb.operationSchedule[key] && moment(dataFromDb.operationSchedule[key].endTime, 'HH:mm') > maxHour) {
    maxHour = moment(dataFromDb.operationSchedule[key].endTime, 'HH:mm')
  }
})

const hoursBetweenMinAndMax = moment.duration(maxHour.diff(minHour)).asHours()

let hours = new Map();
console.log('Am I a Map? hours', hours) 

let auxHour;

for (let i = 0; i <= hoursBetweenMinAndMax; i++) {
  auxHour = i !== 0 ? moment(minHour).add(i, 'hours') : moment(minHour)
  hours.set(auxHour.format('HH:mm'), 0) 
} // piece of code to get the min and max hour, then loop starting from the min hour and end until max hour: ex: 09:00, 10:00, 11:00...23:00

console.log('Am I a Map? hours', hours) 

    // let reservationPrice = new Map(); 
reservationPrice.set('monday', new Map(hours)) //shallow copy of hours
reservationPrice.set('tuesday', new Map(hours))
reservationPrice.set('wednesday', new Map(hours))
reservationPrice.set('thursday', new Map(hours))
reservationPrice.set('friday', new Map(hours))
reservationPrice.set('saturday', new Map(hours))
reservationPrice.set('sunday', new Map(hours))

console.log('reservationPrice', reservationPrice) // supposed to log with days and hours

console.log('Am I a Map()? reservationPrice', reservationPrice 
instanceof Map) // A Map()
}

const price = Object.entries(dataFromDb.reservationPrice).length === 0 // dataFromDb.reservationPrice is an Object
? reservationPrice // reservationPrice is a Map();
: dataFromDb.reservationPrice // Here is turning an Object

console.log('Do I have days and hours?', price) // is an object, and not a Map();
console.log('Am I a Map()? price', price instanceof Map); //before: A Map() | //now: Now is an object;

this.renderFieldDetails(fieldId.id, price)
}

编辑---

如果我做类似price = Object.entries(fieldInfo.reservationPrice).length !== 0 ? reservationPrice : fieldInfo.reservationPrice

的操作

它变成了Map（），但是它是空的（如果数据库中已经有一些数据），并且在onChange函数下面，由于Map（）为空而发生错误。

handlePriceInput = (e, hour, day) => {
let value = e.target.value

const newFieldReservationPrice = this.state.newFieldReservationPrice
console.log('newFieldReservationPrice is a Map()?', newFieldReservationPrice) //before: A Map() || now: not a Map() anymore

let map;

if (!newFieldReservationPrice instanceof Map) {
  console.log('!== Map')
  console.log('newFieldReservationPrice is a Map()? inside if ()', newFieldReservationPrice)
  if (newFieldReservationPrice[day] && newFieldReservationPrice[day][hour]) {
      newFieldReservationPrice[day][hour] = Number(value)
  } 
} else {
  const newMap = new Map(Object.entries(newFieldReservationPrice)) 
  console.log('newMap', newMap) // A Map()

  map = new Map();
  Object.keys(newFieldReservationPrice).forEach(key => {
      map.set(key, new Map(Object.entries(newFieldReservationPrice[key])));
  });
  console.log('Am I a Map()? map', map)

  const aux = map.get(day)
  console.log('aux day', aux) // A Map()
  aux.set(hour, Number(value)) // Comes as undefined || Cannot read property 'set' of undefined
  console.log('aux set', aux) // A Map()

  map.set(day, aux);
  console.log('what do I have?', map)

}
const isReservationPrice = !newFieldReservationPrice instanceof Map ? newFieldReservationPrice : map
console.log('ggggg', isReservationPrice)

this.setState({
  newFieldReservationPrice: isReservationPrice
})
}

谢谢！：）

Answer 1

您可以将带有JavaScript普通对象作为参数的Object.entries()传递给Map()构造函数，以在新的Map对象中创建键值对。

const o = {a:1, b:2, c:{d:3}};

const map = new Map(Object.entries(o));

console.log(map);

将对象从数据库转换为Map（）

1 个答案: