easyUi根据一个日期给另一日期自动赋值的js

$('#loanbegindate').datebox({
    onSelect:function(date){
    changeDate();
    }    
});

$('#loanterm,#loantermtype').change(function(){
     changeDate();
});


function changeDate(){
        var loantermVal=parseInt($('#loanterm').val());//担保期限
        var pactbegindateVal=$('#loanbegindate').datetimebox("getValue");;//担保开始日期
        var type=$('#loantermtype').val();//担保类型
        if(loantermVal && pactbegindateVal){
            var date = new Date(pactbegindateVal);  
            var year = parseInt(date.getFullYear());
            var month = parseInt(date.getMonth());
            var day = parseInt(date.getDate());
            if(type=='1'){
                year=year+loantermVal;
            }
            else if(type=='2'){
                month=month+loantermVal;
            }
            else if(type=='3'){
                day = day+loantermVal;
            }
            var newDate = new Date(year,month,day);
            $('#loanenddate').datebox("setValue", formatDate(newDate));//担保结束如期          
        } 
    }