When we write the code below in the Firefox web browser bookmark, the result 3 is written to the body of the current page:

javascript:
var x = 2;
x += 1;

To avoid this, it is possible to add var before a new variable called y that takes the value of x:

javascript:
var x = 2;
var y = x += 1;

My code has dozens of variables and it wouldn't be practical to have to create other variables just to avoid the problem.

How can I prevent variable values from being written to the document.body of the page?