Question

I have a webpage made of a lot of PHP and Jquery/javascript

I have a function that runs when a submit button is clicked

$("#yesterday").click(function(){
            var $date = $.datepicker.parseDate('yymmdd','<?php echo $_POST['date']; ?>');
            var julDate = $.datepicker.formatDate('yyoo',new Date($date));
            Number(julDate);
            julDate = julDate - 1;
            String(julDate);
            var $date = $.datepicker.parseDate('yyoo',julDate);
            var julDate = $.datepicker.formatDate('yymmdd',new Date($date));
            var $longDate = $.datepicker.formatDate('DD MM d, yy',new Date($date));
            $("#date").val(julDate);
            $("#longdate").val($longDate);
            $("#orwell_btn").click();
return false;
});

This function works PERFECTLY it reduces the date by 1 and reloads the page and executes my SQL query returnning all the correct info

if I change the fifth line and make the function liek so:

    $("#tomorrow").click(function(){
            var $date = $.datepicker.parseDate('yymmdd','<?php echo $_POST['date']; ?>');
            var julDate = $.datepicker.formatDate('yyoo',new Date($date));
            Number(julDate);
            julDate = julDate + 1;
            String(julDate);
            var $date = $.datepicker.parseDate('yyoo',julDate);
            var julDate = $.datepicker.formatDate('yymmdd',new Date($date));
            var $longDate = $.datepicker.formatDate('DD MM d, yy',new Date($date));
            $("#date").val(julDate);
            $("#longdate").val($longDate);
            $("#orwell_btn").click();
return false;
});

the function doesn’t complete and my page loads but as if it would on the very first load (which I have logic to handle but it should be advancing by 1 day ie doing the opposite of the yesterday button)

seems very odd to me

Answer 1

Number(julDate) returns a number with the parsed value.
It doesn’t actually change anything.

Therefore, julDate + 1 is string concatenation.

You want julDate = Number(julDate).