function flipud2d( x ) {
	var out;
	var i;

	out = [];
	for ( i = x.length-1; i >= 0; i-- ) {
		out.push( x[ i ] );
	}
	return out;
}
Reverses the order of elements along the first dimension of a two-dimensional nested input array.

## Notes

-   The function does **not** perform a deep copy of nested array elements.

@param {ArrayLikeObject<Collection>} x - nested input array
@returns {Array<Collection>} output array

@example
var x = [ [ 1, 2 ], [ 3, 4 ], [ 5, 6 ] ];

var out = flipud2d( x );
// returns [ [ 5, 6 ], [ 3, 4 ], [ 1, 2 ] ]