12 lines
517 B
JavaScript
12 lines
517 B
JavaScript
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Date.prototype.getWeek = function() {
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var date = new Date(this.getTime());
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date.setHours(0, 0, 0, 0);
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// Thursday in current week decides the year.
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date.setDate(date.getDate() + 3 - (date.getDay() + 6) % 7);
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// January 4 is always in week 1.
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var week1 = new Date(date.getFullYear(), 0, 4);
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// Adjust to Thursday in week 1 and count number of weeks from date to week1.
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return 1 + Math.round(((date.getTime() - week1.getTime()) / 86400000
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- 3 + (week1.getDay() + 6) % 7) / 7);
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}
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