js 时间日期相加减

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<script type="text/javascript">initDay();//实例化日期,  初始时间为 为当前时间10天前function initDay(){var nowDate = new Date();var str = nowDate.getFullYear()+"-"+(nowDate.getMonth() + 1)+"-"+nowDate.getDate();document.getElementById("end").value=str;nowDate.setDate(nowDate.getDate() + 10); str = nowDate.getFullYear()+"-"+(nowDate.getMonth() + 1)+"-"+nowDate.getDate();document.getElementById("start").value=str;checkDay();}//时间对比function checkDay(){var s1 = '2012-05-12';s1 = new Date(s1.replace(/-/g, "/"));s2 = new Date();var days = s2.getTime() - s1.getTime();var time = parseInt(days / (1000 * 60 * 60 * 24));alert(time);}</script>