How to set a javascript date variable equal to the result from a report query

Trying to pull a date field value into a javascript variable from a QB table. Right now I am calculating the value of the variable (as shown below)...but I need to modify this script to pull the value from a report in QB which returns a single record in the result. 

Here's part of the code:

 

var queryStr = '';

var dbID = 'xxxxxx';

var payPeriodsTable = 'xxxxxx';

var byDayTable = 'xxxx';

$(document).ready(function(){

var currentTime = new Date();

// I need to replace the line below with code that will set newDate equal to a date field from

// a  QB table. 

var newDate = new Date(currentTime.getFullYear(), currentTime.getMonth()+1,  

 currentTime.getDate() + 4-currentTime.getDay());

 

        var endDate = new Date();

//var newDate = new Date("April 22, 2012");

if( (newDate-currentTime) <=0  ) {

newDate.setDate( newDate.getDate()-7 );

}

       endDate.setDate(newDate.getDate()+13);

$('#new_date').val( newDate.getMonth() + '/' + newDate.getDate() + '/' + newDate.getFullYear() );

$('#end_date').val( endDate.getMonth() +1 + '/' + endDate.getDate() + '/' + endDate.getFullYear() );

$('#start_button').click(function() {

$('#start_button').hide();

$('#please_wait').show();

$("#new_date").attr("disabled", true);

startPopulation();

$('#please_wait').hide();

});

});