function isNegativeInteger( x ) {
	return (floor(x) === x && x < 0.0);
}
Tests if a finite double-precision floating-point number is a negative integer.

@param {number} x - value to test
@returns {boolean} boolean indicating whether the value is a negative integer

@example
var bool = isNegativeInteger( -1.0 );
// returns true

@example
var bool = isNegativeInteger( 0.0 );
// returns false

@example
var bool = isNegativeInteger( 10.0 );
// returns false