Get Checked-Out Status of the File in SharePoint

function getcheckoutStatus(listname, itemid)
{
    var clientContext = SP.ClientContext.get_current();
    if (clientContext != undefined && clientContext != null)
    {
        var webSite = clientContext.get_web();
        this.list = webSite.get_lists().getByTitle(listname);
        this.item = list.getItemById(itemid);
        this.file = this.item.get_file();
        clientContext.load(this.file, 'CheckOutType', 'Name', 'CheckedOutByUser');
        clientContext.executeQueryAsync(Function.createDelegate(this, this.OnLoadSuccess), Function.createDelegate(this, this.OnLoadFailed));
    }
}

function OnLoadSuccess(sender, args)
{
    if (this.file.get_checkOutType() < 2) console.log(this.file.get_name() + " is checked out by " + this.file.get_checkedOutByUser().get_title());
    else console.log(this.file.get_name() + " is not checked out.");
}

function OnLoadFailed(sender, args)
{
    try
    {
        console.log('Error: ' + args.get_message() + '\n' + args.get_stackTrace());
    }
    catch (err)
    {}
}

function injectMethod()
{
    getcheckoutStatus("Site Assets", 4);
}
ExecuteOrDelayUntilScriptLoaded(injectMethod, "sp.js");