i am using SharePoint online , i  have written a code to  create a sites using java script but i am getting null value in SPContext file .
please check the below code..
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<script type="text/JavaScript"
  src="https://rajinfotech.sharepoint.com/Shared%20Documents/jquery-1.12.3.js"></script>
</script>
<script type="text/JavaScript"
  src="https://rajinfotech.sharepoint.com/Shared%20Documents/MicrosoftAjax.js"></script>
<script type="text/javascript">
var clientContext ;
$(function(){
bindButtonClick();
});
function bindButtonClick() {
 $("#btnSubmit").on("click", function (){
  createSite();
});
}
  
    function createSite() {
   var collweb;
    var siteTitle=$("#txtSiteTitle").val();
         alert(siteTitle);
    var siteDesc=$("#txtSiteDescription").val();
    alert(siteDesc);
    var siteUrl=siteTitle.replace(/\s/g, "");
     alert(siteUrl);
   clientContext =new SP.ClientContext();
   alert(clientContext);
    collweb=clientContext.get_web().get_webs();
    alert(collweb);
    var webCreationInfo=new SP.WebCreationInformation();
     
    webCreationInfo.set_title(siteTitle);
    
    webCreationInfo.set_title(siteDesc);
    webCreationInfo.set_language(1033);
    webCreationInfo.set_title(siteUrl);
    webCreationInfo.set_useSamePermissionsAsParentSite(true);
    webCreationInfo.set_webTemplate('STS#0');
    var oNewWebsite=collweb.add(webCreationInfo);
     clientContext.executeQueryAsync(Function.createDelegate(this,onQuerySucceeded),Function.createDelegate(this, this.onQueryFailed)
);
}
function onQuerySucceeded() {
   $("#divResults").html("Site successfully Created!");
}
 function onQueryFailed(sender, args) {
   alert('Request failed. ' + args.get_message() + '\n' +args.get_stackTrace());
}
</script>
<div id="DeleteFile">
<div>
<strong>Enter the Name Of the site:</strong>
<br/>
<input tpe="text" id="txtSiteTitle"/>
</div>
<br/>
<div>
<strong>Enter site Description:</strong>
<br/>
<textarea cols="20" id="txtSiteDescription"></textarea>
</div>
<br/>
<input type="button" id="btnSubmit" value="Submit">
</div>
<div id="divResults"></div>