Increase variable increments of one

The idea is to have image that when i click on it it makes the number below it go up by one. I will post a copy of my html and javascript below.

JAVASCRIPT
function increasedigit(digitnumber) {
var x = document.getElementById(digitnumber).innerHTML;
if (x > 9) {
x++;
}
else
{
x == 0;
}
document.getElementById.innerHTML = x;
}

HTML
<div class="two">
<img onclick="increasedigit(digitone)" class="arrowgeneral"…

Increase variable increments of one