75 lines
2.3 KiB
JavaScript
75 lines
2.3 KiB
JavaScript
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import toDate from '../toDate/index.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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* ### v2.0.0 breaking changes:
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*
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* - [Changes that are common for the whole library](https://github.com/date-fns/date-fns/blob/master/docs/upgradeGuide.md#Common-Changes).
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*
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* - Now, `closestIndexTo` doesn't throw an exception
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* when the second argument is not an array, and returns Invalid Date instead.
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*
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* @param {Date|Number} dateToCompare - the date to compare with
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* @param {Date[]|Number[]} datesArray - the array to search
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* @returns {Number} an index of the date closest to the given date
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* @throws {TypeError} 2 arguments required
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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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* var dateToCompare = new Date(2015, 8, 6)
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* var 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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* var result = closestIndexTo(dateToCompare, datesArray)
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* //=> 1
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*/
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export default function closestIndexTo(dirtyDateToCompare, dirtyDatesArray) {
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if (arguments.length < 2) {
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throw new TypeError('2 arguments required, but only ' + arguments.length + ' present');
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}
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var dateToCompare = toDate(dirtyDateToCompare);
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if (isNaN(dateToCompare)) {
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return NaN;
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}
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var timeToCompare = dateToCompare.getTime();
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var datesArray; // `dirtyDatesArray` is undefined or null
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if (dirtyDatesArray == null) {
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datesArray = []; // `dirtyDatesArray` is Array, Set or Map, or object with custom `forEach` method
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} else if (typeof dirtyDatesArray.forEach === 'function') {
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datesArray = dirtyDatesArray; // If `dirtyDatesArray` is Array-like Object, convert to Array. Otherwise, make it empty Array
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} else {
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datesArray = Array.prototype.slice.call(dirtyDatesArray);
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}
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var result;
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var minDistance;
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datesArray.forEach(function (dirtyDate, index) {
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var currentDate = toDate(dirtyDate);
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if (isNaN(currentDate)) {
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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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var distance = Math.abs(timeToCompare - currentDate.getTime());
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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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