function keys( value ) {
	return Object.keys( Object( value ) );
}
Returns an array of an object's own enumerable property names.

## Notes

-   In contrast to the built-in `Object.keys()`, this function returns an empty array if provided `undefined` or `null`, rather than throwing an error.

@private
@param {*} value - input object
@returns {Array} a list of own enumerable property names

@example
var obj = {
    'beep': 'boop',
    'foo': 3.14
};

var k = keys( obj );
// e.g., returns [ 'beep', 'foo' ]