javascript onload even

I have the following table
table name employee
fields
emp_appDate

emp_Dateofbirth

emp_RetirementDate
I want to use the event on the Report and the function should calculate the years of retirement left when the Report Page is loaded. When I execute the report the Status of page remains loading. How I should resolve this.
I used the following function
var birth = Runner.getControl(pageid, 'emp_Dateofbirth');

var app = Runner.getControl(pageid, 'emp_appDate');

var retire = Runner.getControl(pageid, 'emp_RetirementDate');
function func() {

var now = new Date();

var dateofbirth=new Date(birth.getValue());

var dobyear=dateofbirth.getFullYear();

var yearofapp=new Date(app.getValue());

var appyear=yearofapp.getFullYear();

var YearNow = now.getFullYear();

var ageinyears=YearNow-dobyear;

var yearserved=YearNow-appyear;
if (ageinyears>=60||yearserved>=25)

var leftservice = 0;

else

{

var leftservice = yearsleft();

}

function yearsleft()

{

var a = 60-ageinyears;

var bc = 25-yearserved;
if (a>bc)

return (a);

else

return (bc);

}
retire.setValue(leftservice);

};
retire.on('load', func);
// Place event code here.

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