javascript错误：这不是一个函数

Question

返回值时遇到轻微问题。

所以我目前有一个反应项目，并有一个如下组件：

    <List>
    {bookings.map((booking) =>
      <ListItem
        onChange={onChange}
        id={booking.bookingId}
        overdue = {CheckingStatus.overdueCalculation(booking.bookingEnd)}
        initial={booking.customer.initial.substring(0,1)+booking.customer.lastName.substring(0,1)}
        name={booking.customer.initial +'. '+ booking.customer.lastName}
        reference={'REF: '+booking.bookingReference}
        setStyle={selected!=null && selected.id===booking.bookingId ? true : false}
      />
    )}
  </List>

然而，它在overdue = {CheckingStatus.overdueCalculation(booking.bookingEnd)}

时仍然失败

CheckingStatus.js如下：

import moment from 'moment'

export default class overdueChecker {
   static overdueCalculation = (bookingEnd) => {
    //set 1 to grace period of next day 1am
    var d1 = new Date()
    d1.setDate(d1.getDate() + 1);
    d1.setHours(1)
    d1.setMinutes(0)
    d1.setSeconds(0)
    var d2 = new Date(bookingEnd)

    //determine if overdue
    if(d1.getTime()>d2.getTime()){
        this.setState({warning : true})
    } else {
        this.setState({warning : false})
    }

    //calculate days overdue
    var d1m = moment(d1)
    var d2m = moment(d2)
    var diff = d1m.diff(d2m,'days')
    return diff
  }
}

任何想法

Answer 1

overdueCalculation方法应声明为静态方法。例如

export default class overdueChecker {
     static overdueCalculation = (bookingEnd) => {
        // method body
     }
}