Variable changer

Very simple concept. Dont know how to do it.

my issue is that i want it so a user can change ANY VARIABLE in the project.

like this:

var prompt('what variable do you want to change?') = parseInt(prompt('what is the variable value?'));

i attempted this.
the only issue is that i have to do each variable as a if statement.
switch statements wont work for some reason.

This might help:

window[prompt("Name of variable","Name")] = prompt("Enter value here","value")

(Thank you pk)