Question

So far I am trying with:

var myBoolean = false; // global

function toggleBoolean(vr) {
    vr = !vr;
}

alert(myBoolean); // false
toggleBoolean(myBoolean);
alert(myBoolean); // false

But obviously, It failed.

Edit: sorry, I forgot to point out that I want the function to work with many Booleans and not just one

Answer 1

Yes, you can toggle a global boolean from a function. You can’t do it as in your attempt because JavaScript is strictly call-by-value.

function toggleBoolean() {
  myBoolean = ! myBoolean;
}

Now, if you want to toggle a global by name, you could do this (though it’s a little icky):

function toggleBoolean(name) {
  window[ name ] = ! window[ name ];
}

Global variables (in JavaScript on a browser) are properties of the global object, which is known as “window”. In other contexts there are ways of associating a name with the global context. You’d call that function, therefore, like this:

toggleBoolean( "myBoolean" );

Note that I pass a string there instead of a reference to the actual global variable.