How do I run this JSOM

Question

I was looking for ways I can automatically change the content type of my files inside SharePoint online. I go a code from Here

I'm not sure how the code is supposed to work. Added a Webpart, scripteditor on my document library.

At the part in the code where is says contenttypeId, I've pasted the content type id I want the files to be change to.

Nothing is happening. Not sure how the code is supposed to work.

Here is the code:

 var contenttypeId = '0x01040005B1FCA568800F4FB4162C7A09742E67';
var lisTitle = "TestNewList";
var listitemId = 1;

UpdateListItem(lisTitle, listitemId, contenttypeId);

function UpdateListItem(listTitle, listitemId, contenttypeId) {
    var clientContext = new SP.ClientContext();
    oList = clientContext.get_web().get_lists().getByTitle(listTitle);
    oListItem = oList.getItemById(listitemId);
    oListItem.set_item('ContentTypeId', contenttypeId);
    oListItem.update();
    clientContext.load(oListItem, 'Id', 'Title', 'ContentTypeId');
    clientContext.executeQueryAsync(
        Function.createDelegate(this, function() {
            var listsInfo = '';
            listsInfo += oListItem.get_item('Title') + '\t' + oListItem.get_item('ContentTypeId');
            console.log(listsInfo.toString());
        }),
        Function.createDelegate(this, function(sender, args) {
            console.log('Request failed. ' + args.get_message() + '\n' + args.get_stackTrace());
        })
    );
}

Answer 1

Before running the code snippet, need to enable the Content Type Management for the library and add the Content Type needed in library settings,for example, I want to set Content Type "Images" for Item 7 which is an image:

Also, make sure passed valid list name and item Id in the code snippet, this is my test snippet(item Id: 7, list name: doc2):

<script type="text/javascript" language="javascript">
ExecuteOrDelayUntilScriptLoaded(runCode, "sp.js");
function runCode(){   
    var contenttypeId = '0x0101009148F5A04DDD49CBA7127AADA5FB792B00AADE34325A8B49CDA8BB4DB53328F2140047E654AF66AF2C4699BC331533868D61';
    var lisTitle = "doc2";
    var listitemId = 7;

    UpdateListItem(lisTitle, listitemId, contenttypeId);
}
function UpdateListItem(listTitle, listitemId, contenttypeId) {
    var clientContext = new SP.ClientContext();
    oList = clientContext.get_web().get_lists().getByTitle(listTitle);
    oListItem = oList.getItemById(listitemId);
    oListItem.set_item('ContentTypeId', contenttypeId);
    oListItem.update();
    clientContext.load(oListItem, 'Id', 'Title', 'ContentTypeId');
    clientContext.executeQueryAsync(
        Function.createDelegate(this, function() {
            var listsInfo = '';
            listsInfo += oListItem.get_item('Title') + '\n' + oListItem.get_item('ContentTypeId');
            alert(listsInfo.toString());
        }),
        Function.createDelegate(this, function(sender, args) {
            alert('Request failed. ' + args.get_message() + '\n' + args.get_stackTrace());
        })
    );
}
</script>