Add some AJAX to my WP page

I’ve searched the forum, because I can’t believe this is the first time this has come up but I can’t seem to find an answer. I’m creating a page and I want to insert some AJAX code into it. My code is below. It’s a simple script that uses a dropdown to display specific HTML source inside this page depending upon the option selected.

When I upload this code to WP, and look at the source in a browser, it changes the single quotes to &#8217 and ‘ In any event it does not work.

My page is here: https://heronsglenfitness.com/blog/?page_id=3

<script language="javascript">
 var XMLHttpRequestObject = false;
 if (window.XMLHttpRequest) {
 XMLHttpRequestObject = new XMLHttpRequest();
 } else if (window.ActiveXObject) {
 XMLHttpRequestObject = new ActiveXObject("Microsoft.XMLHTTP");
 }
 function getData(dataSource, divID)
 {
 if(XMLHttpRequestObject) {
 var obj = document.getElementById(divID);
 XMLHttpRequestObject.open("GET", dataSource); 

 XMLHttpRequestObject.onreadystatechange = function()
 {
 if (XMLHttpRequestObject.readyState == 4 &&
 XMLHttpRequestObject.status == 200) {
		obj.innerHTML=XMLHttpRequestObject.responseText;

 }
	 if (XMLHttpRequestObject.readyState == 1)
	 {
	 	obj.innerHTML="generating scorecard...";
	 }
 } 

 XMLHttpRequestObject.send(null);
 }
 }
function getScorecard(sel)
{
	var team = sel.options[sel.selectedIndex].value;
	if (team == 1) 	{ getData('aaa.htm', 	'targetDiv') }
	if (team == 2) 	{ getData('bbb.htm', 	'targetDiv') }
	if (team == 3) 	{ getData('ccc.htm', 	'targetDiv') }
}
 </script>

<form action="" method="post">
<table align="center" border="0" cellpadding="8" width="680"><tbody><tr><td align="right"><b>Team:</b></td><td align="left"><select id="dhtmlgoodies_country" name="team" onchange="getScorecard(this)"><option value="" selected>Select a team</option>
<option value="1">aaa</option>
<option value="2">bbb</option>
<option value="3">ccc</option>
</select></td></tr><tr><td colspan="3" align="middle"><b>
<div id="targetDiv"></div>
</b><br /></td></tr></tbody></table>
</form>