Shorthand if/else statement Javascript

I'm wondering if there's a shorter way to write this:

var x = 1;
if(y != undefined) x = y;

I initially tried x = y || 1, but that didn't work. What's the correct way to go about this?

var x = y !== undefined ? y : 1;

Note that var x = y || 1; would assign 1 for any case where y is falsy (e.g. false, 0, ""), which may be why it "didn't work" for you. Also, if y is a global variable, if it's truly not defined you may run into an error unless you access it as window.y.

As vol7ron suggests in the comments, you can also use typeof to avoid the need to refer to global vars as window.<name>:

var x = typeof y != "undefined" ? y : 1;

Another way to write it shortly

bePlanVar = !!((bePlanVar == false));

// is equivalent to

bePlanVar = (bePlanVar == false) ? true : false;

// and 

if (bePlanVar == false) {
    bePlanVar = true;
} else {
    bePlanVar = false;
}

y = (y != undefined) ? y : x;

The parenthesis are not necessary, I just add them because I think it's easier to read this way.

Other way is using short-circuit:

x = (typeof y !== 'undefined') && y || 1

Although I myself think that ternary is more readable.