Prevent JavaScript from treating numbers as strings when using '+'

Sometimes when using JavaScript for calculations, JS treats numbers as string when I use + (addition). If this happens, you can use - (subtraction) and multiply with -1 (negative 1). This forces JS to treat the number string as a number. Very useful in loops, and when getting the number string from e.g. window.document.all.elemID.innerText

: var a=window.
document.all
var total=a(id1).innerText-
(a(id2).innerText*-1)
alert(total)