安装 date-fns 依赖项后出现错误

Question

使用 > "npm install date-fns --save" 安装 date-fns 后出现此错误

尝试导入错误：“date-fns”不包含默认导出（导入为“dateFns”）。

我正在寻找一些解决方案，我需要更改我的导入名称但仍然无法正常工作。有人可以帮忙吗？

这是我的代码

import React, { useState } from "react";
import dateFns from "date-fns";
import "./Calendar.scss";

const Calendar = () => {
  const [currentDate, setCurrentDate] = useState(new Date());
  const [selectedDate, setSelectedDate] = useState(new Date());
  const header = () => {
    const dateFormat = "MMMM YYYY";
    return (
      <div className="header row flex-middle">
        <div className="column col-start">
          <div className="icon" onClick={prevMonth}>
            chevron_left
          </div>
        </div>
        <div className="column col-center">
          <span>{dateFns.format(currentDate, dateFormat)}</span>
        </div>
        <div className="column col-end">
          <div className="icon" onClick={nextMonth}>
            chevron_right
          </div>
        </div>
      </div>
    );
  };
  const days = () => {
    const dateFormat = "ddd";
    const days = [];
    let startDate = dateFns.startOfWeek(currentDate);
    for (let i = 0; i < 7; i++) {
      days.push(
        <div className="column col-center" key={i}>
          {dateFns.format(dateFns.addDays(startDate, i), dateFormat)}
        </div>
      );
    }
    return <div className="days row">{days}</div>;
  };
  const cells = () => {
    const monthStart = dateFns.startOfMonth(currentDate);
    const monthEnd = dateFns.endOfMonth(monthStart);
    const startDate = dateFns.startOfWeek(monthStart);
    const endDate = dateFns.endOfWeek(monthEnd);
    const dateFormat = "D";
    const rows = [];
    let days = [];
    let day = startDate;
    let formattedDate = "";
    while (day <= endDate) {
      for (let i = 0; i < 7; i++) {
        formattedDate = dateFns.format(day, dateFormat);
        const cloneDay = day;
        days.push(
          <div
            className={`column cell ${
              !dateFns.isSameMonth(day, monthStart)
                ? "disabled"
                : dateFns.isSameDay(day, selectedDate)
                ? "selected"
                : ""
            }`}
            key={day}
            onClick={() => onDateClick(dateFns.parse(cloneDay))}
          >
            <span className="number">{formattedDate}</span>
            <span className="bg">{formattedDate}</span>
          </div>
        );
        day = dateFns.addDays(day, 1);
      }
      rows.push(
        <div className="row" key={day}>
          {" "}
          {days}{" "}
        </div>
      );
      days = [];
    }
    return <div className="body">{rows}</div>;
  };
  const nextMonth = () => {
    setCurrentDate(dateFns.addMonths(currentDate, 1));
  };
  const prevMonth = () => {
    setCurrentDate(dateFns.subMonths(currentDate, 1));
  };
  const onDateClick = (day) => {
    setSelectedDate(day);
  };
  return (
    <div className="calendar">
      <div>{header()}</div>
      <div>{days()}</div>
      <div>{cells()}</div>
    </div>
  );
};
export default Calendar;

Answer 1

进口是原因。该库不会导出单个“东西”。

因此，您不能按照您的方式导入它。这就是你应该如何使用它：

// just an example
import { format, startOfWeek, addDays, subDays } from 'date-fns'

// usage example
<div className="column col-center" key={i}>
    {format(addDays(startDate, i), dateFormat)}
</div>

简而言之，直接导入你需要的就行了:)

或者，您可以这样尝试（将所有内容作为对象导入）：

import * as dateFns from "date-fns";

应该也可以工作，您不需要对代码进行任何其他更改。

最后，好好解释一下JS导入/导出here。可能值得检查。）