Elegant way to init and extend a javascript array

Question

Is there a sweet way to init an array if not already initilized? Currently the code looks something like:

if (!obj) var obj = [];
obj.push({});

cool would be something like var obj = (obj || []).push({}), but that does not work :-(

Answer 1

var obj = (obj || []).push({}) doesn't work because push returns the new length of the array. For a new object, it will create obj with value of 1. For an existing object it might raise an error - if obj is a number, it does not have a push function.

You should do OK with:

var obj = obj || [];
obj.push({});