jQuery,格式日期显示的格式不正确

我想显示所选月份第一天的日期,但日期的格式没有显示正确的格式。

我想这样展示 01/11/2017 但它是这样显示的

2017年11月1日星期三00:00:00 GMT+0100(CET)

Select a Date: <input type="date" id="theDate" onmouseout="getTheDays()"/>
<p>First Day of the Month: <label id="fday"></label></p>
<p>Last Day of the Month: <label id="lday"></label></p>

<script>
    function getTheDays() {

        var dt = new Date($('#theDate').val());

        // GET THE MONTH AND YEAR OF THE SELECTED DATE.
        var month = dt.getMonth(),
            year = dt.getFullYear();

        // GET THE FIRST AND LAST DATE OF THE MONTH.
        var FirstDay = new Date(year, month, 1);
        var LastDay = new Date(year, month + 1, 0);

        // FINALLY, GET THE DAY.
        var weekday = new Array();
        weekday[0] = "Sunday";
        weekday[1] = "Monday";
        weekday[2] = "Tuesday";
        weekday[3] = "Wednesday";
        weekday[4] = "Thursday";
        weekday[5] = "Friday";
        weekday[6] = "Saturday";


        if (typeof weekday[FirstDay.getDay()] != 'undefined') {     // CHECK FOR 'undefined'.
            $('#fday').html(FirstDay.toString('dd-MM-yy'));
        }
        else {
            $('#fday').text('');
            $('#lday').text('');
        }
    }
</script>