Question

我有这个数组：

        super(props);
        this.state = {
            data: [{
                baseCurrency: 'GBP',
                baseAmount: 0,
                convertToCurrency: 'USD',
                rates: [],
                currencies: []
            },
                ]
        }

当我尝试在render（）函数中访问它时，出现错误

const {currency，rates，baseCurrency，baseAmount，convertToCurrency} = this.state.data;

const result = Number.parseFloat（baseAmount * rates [convertToCurrency]）。toFixed（2）;

如果我不使用数组声明this.state，则不会发生此问题。

Answer 1

您只能传播特定的对象，因为this.state.data是一个数组：

const [
  { currencies, rates, baseCurrency, baseAmount, convertToCurrency },
] = this.state.data;

更具可读性：

const [firstItem] = this.sate.data;
const {
  currencies,
  rates,
  baseCurrency,
  baseAmount,
  convertToCurrency,
} = firstItem;

Answer 2

像这样解构数据

let res = {
  data: [{
    baseCurrency: 'GBP',
    baseAmount: 0,
    convertToCurrency: 'USD',
    rates: [],
    currencies: []
  }, ]
}

const {
  data: [{
    baseCurrency,
    baseAmount,
    convertToCurrency
  }]
} = res;

console.log(baseCurrency, baseAmount, convertToCurrency);

TypeError：无法读取未定义的属性“未定义”

2 个答案: