Search code examples
javascriptbooleanswitch-statementgate

Or gate (||) sorts false as undefined

I have a code like this:

var IFS =
    document.isFullScreen || 
    document.webkitIsFullScreen || 
    document.mozIsFullScreen || 
    document.msIsFullScreen;

The exact problem is that the || gates sorts false as undefined, since isFullScreen is a boolean.

How do I fix this?

Solution

  • If every element is undefined, then IFS will be undefined. Since undefined is a falsy value, you can still make conditional statements as:

    var IFS =
    document.isFullScreen || 
    document.webkitIsFullScreen || 
    document.mozIsFullScreen || 
    document.msIsFullScreen;

if(!IFS){
    console.log('not full screen');
}

    If you still want to hold the false value in case every other variable is undefined, then you can go with something like: 

    var IFS =
    document.isFullScreen || 
    document.webkitIsFullScreen || 
    document.mozIsFullScreen || 
    document.msIsFullScreen || 
    false;