javascript - use populated array

Is there a one-liner code where I can say the assigning of a variable is to a populated array from a choice of 2 array?

For example:

I'd like:

var myArray = ['a','b','c'];

The choice is between 2 arrays.

var a = [];
var b = ['a','b','c'];

So basically if var a is populated, I'd like myArray to = a. If var a is not populated but var b is populated, myArray = b; if var a and b are empty, then myArray = [];

I've tried the following to no avail:

var myArray = a || b || [];