How to force JS to do math instead of putting two strings together [duplicate]
Solution 1:
You have the line
dots = document.getElementById("txt").value;
in your file, this will set dots to be a string because the contents of txt is not restricted to a number.
to convert it to an int change the line to:
dots = parseInt(document.getElementById("txt").value, 10);
Note: The 10 here specifies decimal (base-10). Without this some browsers may not interpret the string correctly. See MDN: parseInt.
Solution 2:
the simplest:
dots = dots*1+5;
the dots will be converted to number.