C ++中最大的特征值（和相应的特征向量）(Largest eigenvalues (and corresponding eigenvectors) in C++)

 首先你需要让你的js代码处于文档准备就绪状态， 
 
 有一个事件会在您完成时间后执行，您可以使用该事件来提交表单。 看看文本为finish.countdown的行 
 
 尝试下面的代码。 
 
$(document).ready(function(){
    function get15dayFromNow() {   

       return new Date(new Date().valueOf() + <?php echo $duration ; ?> * 60 * 1000);

           }

       var $time_spend = $('#time_spend');
          $time_spend.countdown(get15dayFromNow(), function(event) {
            $(this).val(event.strftime('%M:%S'));
          });

       var $clock = $('#clock');
        $clock.countdown(get15dayFromNow(), function(event) {
            $(this).html('Time Left :   '+'00:'+event.strftime('%M:%S'));
        })
        .on('finish.countdown', function() {
            submitForm();
        });

    function submitForm()
    {
        document.getElementById("target").submit();

    }
});
 
 详细了解文档 

First of all you need to keep you js code in document ready function,
 
There is an event which will execute on completion of your time, you can use that event to submit the form. Look at the line having text as finish.countdown
 
Try following code.
 
$(document).ready(function(){
    function get15dayFromNow() {   

       return new Date(new Date().valueOf() + <?php echo $duration ; ?> * 60 * 1000);

           }

       var $time_spend = $('#time_spend');
          $time_spend.countdown(get15dayFromNow(), function(event) {
            $(this).val(event.strftime('%M:%S'));
          });

       var $clock = $('#clock');
        $clock.countdown(get15dayFromNow(), function(event) {
            $(this).html('Time Left :   '+'00:'+event.strftime('%M:%S'));
        })
        .on('finish.countdown', function() {
            submitForm();
        });

    function submitForm()
    {
        document.getElementById("target").submit();

    }
});
 
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