Delete list item using  JSOM :

Delete Folder Also uisng same code.

function deleteListItem() {

    this.itemId = 2;

    var clientContext = new SP.ClientContext.get_current();;
    var oList = clientContext.get_web().get_lists().getByTitle('ListTitle');

    this.oListItem = oList.getItemById(itemId);

    oListItem.deleteObject();

    clientContext.executeQueryAsync(Function.createDelegate(this, this.onQuerySucceeded),

 Function.createDelegate(this, this.onQueryFailed));
}

function onQuerySucceeded() {

    alert('Item deleted: ' + itemId);
}

function onQueryFailed(sender, args) {

    alert('Request failed. ' + args.get_message() );
}