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32 lines
1.0 KiB
32 lines
1.0 KiB
var getISOYear = require('../get_iso_year/index.js') |
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var startOfISOWeek = require('../start_of_iso_week/index.js') |
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/** |
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* @category ISO Week-Numbering Year Helpers |
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* @summary Return the start of an ISO week-numbering year for the given date. |
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* |
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* @description |
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* Return the start of an ISO week-numbering year, |
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* which always starts 3 days before the year's first Thursday. |
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* The result will be in the local timezone. |
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* |
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* ISO week-numbering year: http://en.wikipedia.org/wiki/ISO_week_date |
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* |
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* @param {Date|String|Number} date - the original date |
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* @returns {Date} the start of an ISO year |
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* |
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* @example |
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* // The start of an ISO week-numbering year for 2 July 2005: |
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* var result = startOfISOYear(new Date(2005, 6, 2)) |
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* //=> Mon Jan 03 2005 00:00:00 |
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*/ |
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function startOfISOYear (dirtyDate) { |
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var year = getISOYear(dirtyDate) |
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var fourthOfJanuary = new Date(0) |
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fourthOfJanuary.setFullYear(year, 0, 4) |
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fourthOfJanuary.setHours(0, 0, 0, 0) |
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var date = startOfISOWeek(fourthOfJanuary) |
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return date |
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} |
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module.exports = startOfISOYear
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