显示选定的单词[Javascript]

Question

用鼠标单击时，句子中的单词会突出显示。它在这里工作。

但; 不幸的是，用按钮显示所选的单词是行不通的。

JSFiddle

words = [];

var sentence = $('.sentence').html().split(/\s+/),

  result = [];

for (var i = 0; i < sentence.length; i++) {

  result[i] = '<span>' + sentence[i] + '</span>';

  var a = sentence[i];

}

$('.sentence').html(result.join(' '));

if (a.indexOf(" ") + 1) {

  alert('fail: ' + a);

} else {

  words.push(a);

}

$('.sentence').on('click', 'span', function() {

  $(this).addClass('highlight');

});

$('button').click(function() {

  alert(words);

});

$('$selectedWords').innerHTML = words;

.sentence span:hover,

.highlight {

  background: red;

}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

<p class="sentence">Lorem ipsum dolor sit amet, consectetur adipisicing elit. Similique aliquam totam odit excepturi reiciendis quam doloremque ab eius quos maxime est deleniti praesentium. Quia porro commodi blanditiis iure dicta voluptatibus.</p>

Selected words:

<p id="selectedWords"></p>

<button>Show in alert</button>