Javascript: localStorage paralyzes if-statements?

Made a boolean variable "disableReplaceDate", used in if-statements. Have to save the variable somehow because the page reloads and I need to use it to "check a status" sort of, so it doesn't return to default every time the page reloads.

Then, to save myself a lot of time and trouble, because I can't send them in the URL as parameters(it's occupied already by a complicated java file which manipulates it all and I'm no good at java at all), I decided to use window.localStorage setItem, getItem and removeItem etc., so basically

 var disableReplaceDate = false;
 window.localStorage.setItem("dRD", false);
 disableReplaceDate = window.localStorage.getItem("dRD");

But now the if-statement, which looked as follows:

 if(disableReplaceDate == true){/*do some stuff*/}

didn't work anymore! But then when I changed it to

 if(disableReplaceDate){/*do some stuff*/}

It starts working suddenly.

And if that wasn't uncanny enough, it won't do this for all if-statements using the variable, I tried changing them to (!disableReplaceDate) and such, but it doesn't make them work.

Why is this? And how do I solve it?