JavaScript function which checks the count of words in a string

var sentence = document.querySelector('#sentence');
var exec = document.querySelector('#exec');
var result = document.querySelector('#result');

// ## THE ACTUAL FUNCTION ###########
// ## Rest is just for testing ######

// Reports the count of words which are 
//   contained in assigned string.

// Parameter (sentence): Are string is 
//   expected. The string doesn't have 
//   to be empty. It has to consist of
//   other characters then just blanks.

// Return a number: The count of words
//   in the assigned string.
//   In case of an error -1 is returned.

function getCountOfWords(sentence) {
  if (sentence.length === 0 || 
      sentence.search(/\w+/) === -1) 
    return -1;

  if (sentence.search(/\s+/) === -1)
    return 1;

  return (sentence.match(/(^|\s)\w+/g)).length;
}

// ## END ACTUAL FUNCTION ###########

function execHandler() {
  result.value = getCountOfWords(sentence.value);
}

exec.addEventListener('click', execHandler);	

.wrap {
  margin: 20px auto;
  width: 900px;
}

.wrap label {
  display: inline-block;
  width: 150px;
}

.wrap div {
  margin: 20px 0;
}

<div class="wrap">
  <div>
    <label for="sentence">
      Sentence to check:
    </label>
    <input type="text" id="sentence" 
           value="one Two2 Three 4four five123"
           size="80" />
  </div>
  <div>
    <button id="exec">Exec</button>
  </div>
  <div>
    <label for="sentence">
      Count of words:
    </label>
    <input type="text" id="result" />
  </div>
</div>