bc518174
 王天杨
提交两个项目文件
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import { addMonths, differenceInCalendarMonths, startOfMonth } from 'date-fns';
/**
* Returns the next previous the user can navigate to, according to the given
* options.
*
* Please note that the previous month is not always the previous calendar
* month:
*
* - if before the `fromDate` date, is `undefined`;
* - if the navigation is paged, is the number of months displayed before.
*
*/
export function getPreviousMonth(
startingMonth: Date,
options: {
numberOfMonths?: number;
fromDate?: Date;
toDate?: Date;
pagedNavigation?: boolean;
today?: Date;
disableNavigation?: boolean;
}
): Date | undefined {
if (options.disableNavigation) {
return undefined;
}
const { fromDate, pagedNavigation, numberOfMonths = 1 } = options;
const offset = pagedNavigation ? numberOfMonths : 1;
const month = startOfMonth(startingMonth);
if (!fromDate) {
return addMonths(month, -offset);
}
const monthsDiff = differenceInCalendarMonths(month, fromDate);
if (monthsDiff <= 0) {
return undefined;
}
// Jump back as the number of months when paged navigation
return addMonths(month, -offset);
}
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