function fibonacci( n ) {
	if (
		isnan( n ) ||
		isInteger( n ) === false ||
		n < 0 ||
		n > MAX_FIBONACCI
	) {
		return NaN;
	}
	return FIBONACCI[ n ];
}
Computes the nth Fibonacci number.

@param {NonNegativeInteger} n - the Fibonacci number to compute
@returns {NonNegativeInteger} Fibonacci number

@example
var y = fibonacci( 0 );
// returns 0

@example
var y = fibonacci( 1 );
// returns 1

@example
var y = fibonacci( 2 );
// returns 1

@example
var y = fibonacci( 3 );
// returns 2

@example
var y = fibonacci( 4 );
// returns 3

@example
var y = fibonacci( 5 );
// returns 5

@example
var y = fibonacci( 6 );
// returns 8

@example
var y = fibonacci( NaN );
// returns NaN

@example
var y = fibonacci( 3.14 );
// returns NaN

@example
var y = fibonacci( -1.0 );
// returns NaN