function offset( x ) {
	var st;
	var sh;
	var o;

	o = x.offset;
	if ( typeof o === 'number' ) {
		return o;
	}
	sh = x.shape;
	if ( sh.length === 0 ) {
		return 0;
	}
	st = x.strides;
	if ( typeof st !== 'object' || st === null ) {
		return 0;
	}
	return strides2offset( sh, st );
}
Returns the index offset specifying the underlying buffer index of the first iterated ndarray element.

@param {ndarrayLike} x - input ndarray
@returns {NonNegativeInteger} index offset

@example
var zeros = require( '@stdlib/ndarray/zeros' );

var n = offset( zeros( [ 3, 3, 3 ] ) );
// returns 0