javascript - ×类型错误: Cannot read property 'borders' of undefined

Question

不确定为什么会收到此错误:

render() {
  14 |   let { params } = this.props.match
  15 |   let country = this.state.countries.find(country => country.cca· === params.id)
> 16 |   let countryBorders = country.borders.map(border => this.state.countries.find(country => country.cca3 === border && country))
 | ^  17 | 

18 |返回 ( 19 | 19

Answer 1

国家的值(value)是什么？您需要确保您没有尝试访问尚不存在的值的属性。

尝试这样的事情:

countryBorders = country && country.borders.map(border => this.state.countries.find(country => country.cca3 === border && country)) || []