Can't update data-attribute value

Question

Although there are some examples about this on the web, it does not seem to work correctly. I can\'t figure out the problem.

I have this simple html

Answer 1

THE ANSWER BELOW IS THE GOOD ONE

You aren't using the data method correctly. The correct code to update data is:

$('#foo').data('num', num); 

So your example would be:

var num = $('#foo').data("num") + 1;       
console.log(num)       
$('#foo').data('num', num); 
console.log(num)