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javascript - 如何迭代 Map() 对象？

问题描述

我有一个需要迭代的 Map() 对象，因此我可以获得星期几和选定的时间。下面的代码不起作用，因为Object.keys(newFieldReservationPrice).forEach它试图循环一个 Map() 对象，这似乎没有意义。那么，有没有更好的解决方案呢？

下面是代码：

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

const newFieldReservationPrice = this.state.newFieldReservationPrice
console.log('newFieldReservationPrice', newFieldReservationPrice) // A Map();
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 {
  map = new Map();
  console.log('map object', Object.keys(newFieldReservationPrice)) // logs map object []

  Object.keys(newFieldReservationPrice).forEach(key => {
    console.log('key', key)
      map.set(key, new Map(Object.entries(newFieldReservationPrice[key])));
  }); // This doesn't work
  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('isReservationPrice', isReservationPrice)

this.setState({
  newFieldReservationPrice: isReservationPrice
})
}

谢谢！:)

标签： javascriptreactjs

解决方案

您可以使用以下方法迭代Map对象for of：

for (const [key, value] of myMap) {
  console.log(key, value);
}

这与遍历条目相同：

for (const [key, value] of myMap.entries()) {
  console.log(key, value);
}

正如@Nina Scholz 所说，您可以forEach在Map原型（doc MDN）上使用：

myMap.forEach((value, key, map) => {
  console.log(key, value);
}

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