javascript 日期判断比较大小

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转载最新推荐文章于 2026-09-24 12:18:24 发布 436 阅读 AI 写同款· GEO 优化 ›

JavaScript中日期大小比较的全面教程时间戳是一个广泛应用于计算机领域的概念，它是一个自特定起始点（称为纪元，epoch）以来所经过的毫秒数。在JavaScript中，getTime()方法返回的时间戳就是相对于1970年1月1日 UTC午夜的时间长度，它是衡量时间间隔的统一标准。使用时间戳进行日期比较的重要性在于，它避免了因为日期格式化或者不同时间单位（如时、分、秒）造成的比较复杂性。当两个日期对象转换为时间戳后，你可以直接使用简单的数字比较来确定它们之间的先后关系，这在进行大量日期比较时尤其高效。阅读详情

文本框的内容改变时另一个下拉列表框随着改变
下面的例子是输入出生日期，然后星座下拉框相应变动：

<intpu type="text" id="aa" value="1982-08-24" onchange="birthChange(this)/>
<script type="text/javascript">
            function birthChange(obj){
                if(obj!=null){
                    var da = obj.value.split("-");
                    if(da.length==3){
                        var index = getConstellationIndex(da[1],da[2]);
                        document.getElementById("ctl00_cphBody_ddlConstellation").selectedIndex = index;
                    }
                }
            }
            function getConstellationIndex(month, day){
                var year = "2009";
                var result = -1;
                var d = new Date(year,month,day);
                var min = new Date(year,"1","20");
                var max = new Date(year,"2","18");
                if(d>=min && d<=max){
                    result = 0;
                }
                min = new Date(year,"2","19");
                max = new Date(year,"3","20");
                if(d>=min && d<=max){
                    result = 1;
                }
                min = new Date(year,"3","21");
                max = new Date(year,"4","19");
                if(d>=min && d<=max){
                    result = 2;
                }
                min = new Date(year,"4","20");
                max = new Date(year,"5","20");
                if(d>=min && d<=max){
                    result = 3;
                }
                min = new Date(year,"5","21");
                max = new Date(year,"6","20");
                if(d>=min && d<=max){
                    result = 4;
                }
                min = new Date(year,"6","21");
                max = new Date(year,"7","22");
                if(d>=min && d<=max){
                    result = 5;
                }
                min = new Date(year,"7","23");
                max = new Date(year,"8","22");
                if(d>=min && d<=max){
                    result = 6;
                }
                min = new Date(year,"8","23");
                max = new Date(year,"9","22");
                if(d>=min && d<=max){
                    result = 7;
                }
                min = new Date(year,"9","23");
                max = new Date(year,"10","22");
                if(d>=min && d<=max){
                    result = 8;
                }
                min = new Date(year,"10","23");
                max = new Date(year,"11","21");
                if(d>=min && d<=max){
                    result = 9;
                }
                min = new Date(year,"11","22");
                max = new Date(year,"12","21");
                if(d>=min && d<=max){
                    result = 10;
                }
                min = new Date(year,"12","22");
                max = new Date(year,"1","19");
                if((d>=min && d<=new Date(year,"12","31")) || (d>=new Date(year,"1","1") && d<=max)){
                    result = 11;
                }
                return result;
            }
            </script>

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