[JavaScript] Array.flatten()

gistfile1.js

function flattenArray() {
	return this.reduce(function(lhs, rhs) {
		// lhs is already flatten.
		if((rhs instanceof Array) && rhs.some(Array.isArray)) rhs = flattenArray.call(rhs);

		return lhs.concat(rhs);
	}, []);
}

gistfile2.js

function test() {
	Array.prototype.flatten = flattenArray;

	Logger.log([].flatten());
	Logger.log([1].flatten());
	Logger.log([1,2].flatten());
	Logger.log([1,2,3].flatten());
	Logger.log([[1],2].flatten());
	Logger.log([1,[2]].flatten());
	Logger.log([1,[2,3]].flatten());
	Logger.log([[1,2],3].flatten());
	Logger.log([[1,2],[3,[4,5]]].flatten());
}