58 lines
1.5 KiB
JavaScript
58 lines
1.5 KiB
JavaScript
import { toDate } from "./toDate.js";
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/**
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* @name closestIndexTo
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* @category Common Helpers
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* @summary Return an index of the closest date from the array comparing to the given date.
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*
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* @description
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* Return an index of the closest date from the array comparing to the given date.
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*
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* @param dateToCompare - The date to compare with
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* @param dates - The array to search
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*
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* @returns An index of the date closest to the given date or undefined if no valid value is given
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*
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* @example
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* // Which date is closer to 6 September 2015?
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* const dateToCompare = new Date(2015, 8, 6)
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* const datesArray = [
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* new Date(2015, 0, 1),
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* new Date(2016, 0, 1),
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* new Date(2017, 0, 1)
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* ]
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* const result = closestIndexTo(dateToCompare, datesArray)
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* //=> 1
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*/
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export function closestIndexTo(dateToCompare, dates) {
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// [TODO] It would be better to return -1 here rather than undefined, as this
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// is how JS behaves, but it would be a breaking change, so we need
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// to consider it for v4.
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const timeToCompare = +toDate(dateToCompare);
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if (isNaN(timeToCompare)) return NaN;
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let result;
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let minDistance;
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dates.forEach((date, index) => {
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const date_ = toDate(date);
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if (isNaN(+date_)) {
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result = NaN;
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minDistance = NaN;
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return;
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}
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const distance = Math.abs(timeToCompare - +date_);
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if (result == null || distance < minDistance) {
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result = index;
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minDistance = distance;
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}
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});
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return result;
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}
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// Fallback for modularized imports:
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export default closestIndexTo;
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