function floorsd( x, n, b ) {
	var exp;
	var s;
	var y;
	if (
		isnan( x ) ||
		isnan( n ) ||
		n < 1 ||
		isInfinite( n ) ||
		isnan( b ) ||
		b <= 0 ||
		isInfinite( b )
	) {
		return NaN;
	}
	if ( isInfinite( x ) || x === 0.0 ) {
		return x;
	}
	if ( b === 10 ) {
		exp = log10( abs( x ) );
	}
	else if ( b === 2 ) {
		exp = exponent( abs( x ) );
	}
	else {
		exp = ln( abs(x) ) / ln( b );
	}
	exp = floor( exp - n + 1.0 );
	s = pow( b, abs( exp ) );

	// Check for overflow:
	if ( isInfinite( s ) ) {
		return x;
	}
	// To avoid numerical stability issues due to floating-point rounding error (e.g., 3.55/0.1-35.5 = -7.105427357601e-15 and 3.55*10-35.5 = 0), we must treat positive and negative exponents separately.
	if ( exp < 0 ) {
		y = floor( x * s ) / s;
	} else {
		y = floor( x / s ) * s;
	}
	// Check for overflow:
	if ( isInfinite( y ) ) {
		return x;
	}
	return y;
}
Rounds a numeric value to the nearest number toward negative infinity with \\(N\\) significant figures.

@param {number} x - input value
@param {PositiveInteger} n - number of significant figures
@param {PositiveInteger} b - base
@returns {number} rounded value

@example
var v = floorsd( 3.141592653589793, 5, 10 );
// returns 3.1415

@example
var v = floorsd( 3.141592653589793, 1, 10 );
// returns 3.0

@example
var v = floorsd( 12368.0, 2, 10 );
// returns 12000.0

@example
var v = floorsd( 0.0313, 2, 2 );
// returns 0.03125