Javascript: inverting a boolean does not work

Question

i am trying to invert a boolean value (toggle);

var current_state=$.cookie('state');
if(current_state==null) {
  current_state=false;
}
console.log(current_state);
current_state=(!current_state);
console.log(current_state);

$.cookie('state', current_state, { expires: 7, path: '/' });

In my opinion the second console.log should display the opposite of the first one, but both calls report false. Whats up here?

Answer 1

Your $.cookie('state') seems to be a string ("false").

As a proof, see the following code (also in this jsfiddle):

var current_state='false';
if(current_state==null) {
  current_state=false;
}
console.log(current_state);
var current_state=(!current_state);
console.log(current_state);

It outputs false twice.

Why? Because you check if it is null and do not support other cases.

You can do something like this:

var current_state='false';
if(current_state==null ||
    current_state==false ||
    current_state=='false') {
    current_state = false;
}else{
    current_state = true;
}
console.log(current_state);
current_state=(!current_state);
console.log(current_state);

and your code will output boolean true or false first and then the opposite boolean value.

Answer 2

Are you sure that in the case that current_state is not null that it is actually a boolean value? Perhaps it's a string?

Answer 3

The problem is that current_state is not a boolean but a string

var current_state=$.cookie('state');
if(current_state==null) {
    current_state=false;
}   

console.log(current_state);
var current_state= current_state == 'false' ? "true" : "false"; // (!current_state);
console.log(current_state);
$.cookie('state', current_state);