如何确保结束日期总是比开始日期多7天？ [英] How to make sure end date is always 7 days more than start date?

问题描述

我有一个页面显示开始日期和结束日期，如下所示：

I have a page that shows the start date and end date like below:

您可以看到，默认情况下，结束日期总是比开始日期多7天。我可以更改开始日期，但是如何确保每次更改开始日期时，结束日期也要分别加上7天？

As you can see the end date is always 7 days more than the start date by default. I am allowed to change the start date but how do I make sure every time I change the start date,the end date also adds up 7 days to the respective start date?

代码：

  <%

        String relPath = "../../../";
        String currentDate = CoreUtil.parseDate(new Date());

        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
        //get current date
        Calendar cal = Calendar.getInstance();
        //Number of Days to add
        cal.add(Calendar.DAY_OF_MONTH, 7);
        String defaultDate = sdf.format(cal.getTime());





    %>

Start Date:&emsp;<input class="txtStartDate" style="font: 13px/1.231 Trebuchet MS;" type="text" id="txtStartDate" name="Start Date" value="<%=currentDate%>" readonly><br><br>


End Date: &emsp; <input class="txtEndDate" style="font: 13px/1.231 Trebuchet MS;" type="text" id="txtEndDate" name="txtEndDate" value="<%=defaultDate%>"  readonly required/>

编辑：

这是我的JavaScript代码：

This is my JavaScript code:

<Script>
    $('#txtStartDate').datepicker();
    $('#txtEndDate').datepicker();

    $('#txtStartDate').change(function(){
        var interval = 7;

        function convertDateString(p) { return (p < 10) ? '0' + p : p; }

        var startDate = new Date($(this).val());
        startDate.setDate(startDate.getDate() + interval);
        $('#txtEndDate').val( startDate.getFullYear() + '/' +     convertDateString(startDate.getMonth() + 1) + '/' + convertDateString(startDate.getDate()));
    });

</script>

基本上，每当我更改开始日期时，结束日期应自动更改为（开始日期+7天），这就是我想要做的。上面的代码应该可以使用，但是当我更改开始日期时，它并没有更改我的结束日期。

Basically whenever I change my start date, the end date should be automatically change to (start date+7 days) as well, that's all I'm trying to do. The above code should have work but it did not change my end date when I changed my start date.

推荐答案

这可能会有所帮助。

Date.prototype.addDays = function(days) {
    var date = new Date(this.valueOf());
    date.setDate(date.getDate() + days);
    return date;
}

$('#txtStartDate').datepicker();
$('#txtEndDate').datepicker();

$('#txtStartDate').change(function(){
    var interval = 7;
    var startDate = new Date($(this).val());
    $('#txtEndDate').val(startDate.addDays(interval));
});

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