在文本框中显示当前星期五的值

i want user open webpage and textbox show value of current friday. i don't know how to use .val here is my code.

$(function() {
$("#dateInput").datepicker({

    //In Datepicker set the Calendar display start with Sunday (by default datepicker starts from Sunday)
    firstDay: 0,

    //Before Populating the Calendar set the Enabled & Disabled Dates using beforeShowDay(Date) function
    beforeShowDay: function (date) {

        //Get today's date
        var sunday = new Date();

        //Set the time of today's date to 00:00:00 
        sunday.setHours(0,0,0,0);

        sunday.setDate(sunday.getDate() - (sunday.getDay() || 0));

        //Set the Date to Sunday
        var saturday = new Date(sunday);
        var thrusday = new Date(sunday);
        var currentday = new Date();

        //0 is sunday 6 is saturday
        var currentdayofweek = currentday.getUTCDay();
        //console.log(currentday, "show currentday");
        //alert('value of currentday=>'+currentday);
        //alert('value of currentday of week=>'+currentdayofweek);
        //location.reload();

        //Now add 6 to Sunday to get the Date of Saturday (End of that Week)
        saturday.setDate(sunday.getDate() + 6);
        //add by kim
        thrusday.setDate(sunday.getDate() + 4);

        //edit by kim
        //return [(date >= thrusday && date <= saturday ), ''];
        // current day of week <5  mean user can select friday only day before friday
        return [(date > thrusday && date < saturday && currentdayofweek < 5), ''];
    }
});
  var temp = $("#dateInput").datepicker("option", "dateFormat", "yy-mm-dd");

  return temp;
});

and here is textbox code.

<input type="text" name="dateInput" id="dateInput"/>

1. i just want user can select only friday of current week in calendar
2. and value of friday in current week should show in text box before user select

This will fill the #dateInput input with the date corresponding to the Friday of the current week.

var date = new Date(),
    day = date.getDay(),
    dif = 5 - day >= 0 ? 5 - day : day - 5;
date.setTime( date.getTime() + (dif * 24 * 60 * 60 * 1000) );
$(document).ready(function() {
    $("#dateInput").val( date.getUTCFullYear() + "/" + (date.getMonth()+1) + "/" + date.getUTCDate() );
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<input type="text" name="dateInput" id="dateInput"/>

</div>

marventus . i mean Format is correct but the date is not current friday that show in textbox. example . user login to system at saturday 2015/1/3 , system should input next friday for user. it should be 2015/1/9 . But your code input value into textbox is 2015/1/4