JS基础知识复习（二）：时间对象及定时器

一：时间对象

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<head><meta charset="UTF-8"><title>Title</title><script type="text/javascript">/*** 日期对象的创建：* 1. Date只能通过new 创建。* 2. 无参时为当前系统时间* 3. 参数格式：*    3.1 new Date("2015/08/22");\*    3.2 new Date("2015-08-22");*    3.2 new Date(2016 , 04 , 13 , 14 , 34);*    3.3 毫秒方式传入，计算从1970年开始 + 毫秒数，计算出时间*/var d = new Date(2016 , 04 , 13 , 14 , 34);alert(d);var d1 = new Date(1000);alert(d1);/*** 日期对象常用格式化方法：* 1.toDateString:星期、日期* 2.toLocaleDateString:* 3. set/getDate:返回一个月中的某一天。* 4. getDay:返回一周中的某一天（从周日开始，至周六。0-6）。* 5. set/getMonth:返回月份* 6. set/getFullYear:返回年份* 7. set/getHours：小时       set/getMinutes：分钟       set/getSeconds：秒数       set/getMilliseconds：毫秒数* 8. set/getTime：返回1970至今的毫秒数* 9. set/getUTC + 以上set/get方法后缀：返回格林尼治日期*/var d2 = new Date();alert(d2.toDateString());alert(d2.toLocaleDateString());alert(d2.getDay());/*** Date.parse()*/var time = Date.parse("2018-10-01");alert(time);alert(new Date(time).toLocaleDateString());/*** 自定义格式输出时间*/function showDate() {var _date = new Date(),_year = _date.getFullYear(),_month = _date.getMonth() + 1,_day = _date.getDate() ,_hours = _date.getHours() ,_minutes = _date.getMinutes() ,_seconds = _date.getSeconds();return _year + "-" + _month + "-" + _day + " " + _hours + ":" + _minutes + ":" + _seconds + " " + showWeek();}function showWeek(){var WEEK_GBK = "周",_date = new Date(),_weekDay = _date.getDay();if (_weekDay == 0){return WEEK_GBK + "日";}else if (_weekDay == 1){return WEEK_GBK + "一";}else if (_weekDay == 2){return WEEK_GBK + "二";}else if (_weekDay == 3){return WEEK_GBK + "三";}else if (_weekDay == 4){return WEEK_GBK + "四";}else if (_weekDay == 5){return WEEK_GBK + "五";}else if (_weekDay == 6){return WEEK_GBK + "六";}};alert(showDate());</script>
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二：定时器 setInterval

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<head><meta charset="UTF-8"><title>Title</title><script type="text/javascript">/*** 定时器：setInterval()* 语法：setInterval(callBack , 毫秒数);* setInterval的返回值是当前定时器的ID*/function showDemo() {document.write("Hello 定时器!<br/>");}window.onload = function () {var timer = setInterval(showDemo , 1000);alert(timer);if (timer == 1){// clearInterval：取消定时器clearInterval(timer);}}</script>
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