JavaScript get current week number

<!DOCTYPE html>
<html>
<body>
	<h2>
		JavaScript函数
	</h2>
	<p>
		本例调用了一个执行计算的函数,然后返回结果:
	</p>
	<p id="demo"></p>
	<script>
		function getWeek(dt) {
			// 默认当前时间
			var d = dt ? new Date(dt) : new Date();
			var day = d.getDay();
			var originDate = d.getFullYear() + '/' + "01" + '/' + "01" + ' 00:00:00';
			var nowDate = d.getFullYear() + '/' + ((d.getMonth() + 1) > 9 ? (d.getMonth() + 1) : '0' + (d.getMonth() + 1)) + "/" + (d.getDate() > 9 ? d.getDate() : '0' + d.getDate()) + ' 00:00:00';
			var nowStrapTime = (new Date(nowDate)).getTime();
			var originStrapTime = (new Date(originDate)).getTime();
			var originDay = ((new Date(originStrapTime)).getDay()) == 0 ? 7 : ((new Date(originStrapTime)).getDay());
			var nowDay = d.getDay() == 0 ? 7 : d.getDay();
			var weeks = 0;
			var resultStrap = 0;
			if (nowDay > originDay) {
				resultStrap = nowStrapTime - (nowDay - originDay) * 1000 * 3600 * 24 - originStrapTime;
				if (resultStrap > 0) {
					weeks = (resultStrap / (3600 * 1000 * 24 * 7)) + 1
				} else {
					weeks = 1
				}
			} else {
				resultStrap = nowStrapTime + (originDay - nowDay) * 1000 * 3600 * 24 - originStrapTime;
				weeks = (resultStrap / (3600 * 1000 * 24 * 7)) + 1
			}
			return weeks
		}
		document.getElementById("demo").innerHTML = getWeek();//当前时间
		//document.getElementById("demo").innerHTML = getWeek('2021-12-31');//指定日期
	</script>
</body>
</html>

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Origin blog.csdn.net/qq285679784/article/details/122317632