Create array and push into it in one line

Question

The following is just a theoretical JavaScript question. I am curious if the following can be converting into a single statement:

if(!window.foo){
  window.foo =         


        

Answer 1

This question got me playing with different options for fun. It's too bad push returns the length instead of the original array reference, but for even shorter expressions it can be helpful to have something that can be immediately iterated, mapped, etc.

window.foo = (window.foo||[]).concat(['bar']); // always returns array, allowing:
(window.foo = (window.foo||[]).concat(['bar'])).forEach( ... )

(window.foo = window.foo||[]).push('bar'); // always returns length

window.foo && window.foo.push('bar') || (window.foo = ['bar']); // playing around