The challenges so far have covered matching letters of the alphabet and numbers. You can also match the whitespace or spaces between letters.
You can search for whitespace using <code>\s</code>, which is a lowercase <code>s</code>. This pattern not only matches whitespace, but also carriage return, tab, form feed, and new line characters. You can think of it as similar to the character class <code>[ \r\t\f\n\v]</code>.
testString: assert(/\\s/.test(countWhiteSpace.source), 'Your regex should use the shorthand character <code>\s</code> to match all whitespace characters.');
testString: assert("Men are from Mars and women are from Venus.".match(countWhiteSpace).length == 8, 'Your regex should find eight spaces in <code>"Men are from Mars and women are from Venus."</code>');
testString: 'assert("Space: the final frontier.".match(countWhiteSpace).length == 3, ''Your regex should find three spaces in <code>"Space: the final frontier."</code>'');'
testString: assert("MindYourPersonalSpace".match(countWhiteSpace) == null, 'Your regex should find no spaces in <code>"MindYourPersonalSpace"</code>');