function at3d( x, i0, i1, i2 ) {
	var x0;
	var x1;
	var N;

	N = x.length;
	if ( i0 < 0 ) {
		i0 += N;
	}
	if ( i0 < 0 || i0 >= N ) {
		return;
	}
	x0 = x[ i0 ];
	N = x0.length;
	if ( i1 < 0 ) {
		i1 += N;
	}
	if ( i1 < 0 || i1 >= N ) {
		return;
	}
	x1 = x0[ i1 ];
	N = x1.length;
	if ( i2 < 0 ) {
		i2 += N;
	}
	if ( i2 < 0 || i2 >= N ) {
		return;
	}
	return x1[ i2 ];
}
Returns an element from a three-dimensional nested array.

@param {ArrayLikeObject<ArrayLikeObject<Collection>>} x - input array
@param {integer} i0 - first dimension index
@param {integer} i1 - second dimension index
@param {integer} i2 - third dimension index
@returns {*} nested array element

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

var v = at3d( x, 0, 0, 1 );
// returns 2

v = at3d( x, 0, 1, 0 );
// returns 3

v = at3d( x, 0, -2, -2 );
// returns 1