I want to change belo url using javascript

From:

<a class='button' href="#" target="_blank" id="download_link" style="display: none;"><i class='icon download'></i>Download Now</a>

To

<a class='button' href="https://google.com" target="_blank" id="download_link" style="display: none;"><i class='icon download'></i>Download Now</a>

My code is

<a class='button' href="#" target="_blank" id="download_link" style="display: none;"><i class='icon download'></i>Download Now</a>
<script type="application/javascript">
 var tURL = "https://google.com"
 var download_link = document.getElementById("download_link");
 download_link.innerHTML.replace("#", tURL);

where I do mistake please correct this. I know it is easy to use hyper link in html. but I want to replace urls using javascript