title: Regex that matches anything except for all whitespace
body: <p>I need a (javascript compliant) regex that will match any string except a string that contains only whitespace. Cases:</p>
  
  <pre><code>" "         (one space) =&gt; doesn't match
  "    "      (multiple adjacent spaces) =&gt; doesn't match
  "foo"       (no whitespace) =&gt; matches
  "foo bar"   (whitespace between non-whitespace) =&gt; matches
  "foo  "     (trailing whitespace) =&gt; matches
  "  foo"     (leading whitespace) =&gt; matches
  "  foo   "  (leading and trailing whitespace) =&gt; matches
  </code></pre>