using jquery and session storage but system crashes

Question

For some university coursework I am trying to use jQuery and sessionStorage so that I can store data across pages, however it crashes when the following line is executed:

eDiffpl = eventDate.getTime() - pageLoadDate.getTime() – benchTime;

error says: Uncaught SyntaxError: Unexpected token ILLEGAL

Here is the full script:

 var pageLoadDate;
 var benchTime;
 var eventDate;
 var eDiffpl;

 $(document).ready(function() {
   pageLoadDate = new Date();

   $("*").click(function(e) {
       // Stop the function propagating up the DOM tree
       e.stopPropagation();

       // Get the interaction time
       eventDate = new Date();

       // <p data-islink="islink">dduiduihd</p>

       // Check if this is the link we want
       if ($(this).data("footballLink") != undefined) {
         // The right link has been clicked
         benchTime = benchmarkDate();

         eDiffpl = eventDate.getTime() - pageLoadDate.getTime()– benchTime;
         sessionStorage.myTester = Number(sessionStorage.myTester) + eDiffpl;

         // Then move to next page of experiment
         window.location.url = "feedback_page.html";
       }
     } else {
       // An incorrect part of the page has been clicked
       sessionStorage.errorCount = Number(sessionStorage.errorCount) ++;
       console.log(sessionStorage.errorCount);
     }
   });
 });

benchmarkDate function:

function benchmarkDate()
{
var start_date;
var end_date;

start_date=new Date(); // 1

// 100
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();

// 200
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();

// 300
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();

// 400
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();

// 500
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();

// 600
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();

// 700
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();

// 800
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();

// 900
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();

// 999
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();
end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date(); end_date=new Date();

var diff = (end_date.getTime() - start_date.getTime());

//Debug line below
//alert("start: " + start_date.getTime() + "\nend: " + end_date.getTime() + "\nDiff: " + diff)

return diff;
}

Answer 1

There are three problems with your code that I can see immediately. The line you get the error on, the second subtraction sign is not a valid subtraction sign. Delete it and retype it. Second. your closures aren't correct, starting with the if else blocks in the click function. Third you aren't using sessionStorage correctly. Setting and getting values involves calling functions on sessionStorage not just adding properties with dot notation

I am not sure what your code is supposed to do but here is a cleaned up version that doesn't give any errors.

$("*").click(function(e) {
    e.stopPropagation();
    eventDate = new Date();
    if ($(this).data("footballLink") != undefined) {
        benchTime = benchmarkDate();

        // Had some unknown character as a minus sign here.
        eDiffpl = eventDate.getTime() - pageLoadDate.getTime() - benchTime;

        // Setting/Getting values with sessionStorage needs to call
        // getItem and setItem passing keys and values
        // sessionStorage.setItem('key', 'value')
        // sessionStorage.getItem('key')
        var value = parseInt(sessionStorage.getItem('myTester'), 10) + eDiffpl;
        sessionStorage.setItem('myTester', value);
        window.location.url = "feedback_page.html";

    // Fixed your closures here.
    } else {
        var myNumber = parseInt(sessionStorage.getItem('errorCount'), 10);
        myNumber++;
        sessionStorage.setItem('errorCount', myNumber);
        console.log(myNumber);
    }
});

I also changed your Number() to parseInt for no reason other than its more familiar to me. And also added some variables to make the code more readable than working directly off sessionStorage constantly. But lastly that unexpected illegal token was whatever character that last minus character was. Besides the error if you look at your example above one minus sign is longer than the other.