As you say:
This works fine. However, it seems that when testing it on mobile there is a small delay. (is TRUE)
The reason is that by default, the browser's waits about 300 ms
for a possible doubleClick/doubleTap event
, before calling the function (hourUse('hours',1);
in this case).
There are some solutions available, check a library called FastClick (Polyfill to remove click delays on browsers with touch UIs).
here is the link: https://github.com/ftlabs/fastclick