function isNonPositiveInteger( x ) {
	return (floor(x) === x && x <= 0);
}
Tests if a finite double-precision floating-point number is a nonpositive integer.

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

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

@example
var bool = isNonPositiveInteger( 0.0 );
// returns true

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