Javascript Addition Not Working

This is probably has a simple answer but I have been working on this for hours without being able to figure it out. I have the following function that retrieves a value ‘spot’ from input field ‘myInput’ and calculates a value ‘tmpspot’. For this example I am entering the number ’23’ in the field “myInput” (type=”number”). When I pass ’23’ to the function as shown below the function properly returns ’44’. However, when I comment out the line “tmpspot = tmpspot – (0 – spot) ;” and instead use the previous line “tmpspot = tmpspot + spot ;”, the function returns ‘2123’, as though it concatenated the two numbers instead of adding them together. What am I missing? function NextSpot() { var spot = document.getElementById(“myInput”).value; var tmpspot = spot % 2 ; tmpspot = (tmpspot – (0 – spot)) – 1 ; tmpspot = 65 – spot ; tmpspot = tmpspot / 2 ; tmpspot = parseInt(tmpspot); // tmpspot = tmpspot + spot ; tmpspot = tmpspot – (0 – spot) ; document.getElementById(“demo”).innerHTML = tmpspot ; return true ; } I realized that php was treating the variables as string variables, not numeric variables. For now, I including the following line to make sure that the variable ‘spot’ is an integer: spot = parseInt(spot) ; The function is now working.