Edit in JSFiddle

$(document).ready(function() {
  $("button").click(function() {
    $("button").text('Thanks for clicking!');
  });
  $("#content a").click(function() {
    alert('HREF Attribute value before: ' + $("#content a").attr('href'));
    $("#content a").attr('href', '##');
    alert('HREF Attribute value after: ' + $("#content a").attr('href'));
  });
});
<h2>jCombat Demo - jQuery DOM Manipulations</h2>

<div id="content">
  <p>This is a paragraph. <a href="#">Sample Link</a></p>
</div>

<button>Click me</button>