Unable to fetch versionItem.get_createdBy().get_title(). Error Title is not initialize. Please help

Question

I have a problem in JSOM code for SharePoint. Below is the description:

When I try to fetch get_createdBy from FileVersion object it returns SP.User object and when I try to fetch user title or loginName ( .get_title() or .get_loginName() ) from SP.User object I get an error that Title nor loginName is not initialize. Below is my code without createdBy and is working fine with no errors and I am able to get all other details from a FileVersion object except createdBy. Any help would be appreciated.

var totalVersions = 0;
var versionDetailsCounter = 0;

function getVersionHistory() {
    var fileVersions = clientContext.get_web().getFileByServerRelativeUrl(_spPageContextInfo.serverRequestPath).get_versions();

    clientContext.load(fileVersions);
    clientContext.executeQueryAsync(Function.createDelegate(this, function () { onGetVersionHistorySuccess(fileVersions); }), onFail);
}

function onGetVersionHistorySuccess(fileVersions) {
    var objlistVersionEnumerator = fileVersions.getEnumerator();
    totalVersions = fileVersions.get_count();        
    vTableHtml = "";

    while (objlistVersionEnumerator.moveNext()) {
        var vItem = objlistVersionEnumerator.get_current();
        vTableHtml += "<tr> <td>" + vItem.get_versionLabel() + "</td> <td>" + formatDate(vItem.get_created(), 2) + "</td> <td>" + vItem.get_checkInComment() + "</td> </tr>";
        versionDetailsCounter++;            
    }

    if (totalVersions === versionDetailsCounter) {
        if (vTableHtml) {
            vTableHtml = "<div id='lblVersionHistory'><h5><strong>Version History</strong></h5></div><table class='table'><thead><tr><th>Version No.</th><th>Modified</th><th>Comments</th></tr></thead><tbody>" + vTableHtml + "</tbody></table>";
            $('#divVersionHistory').html(vTableHtml);
        } else {
            vTableHtml = "Version history not available.";
        }
    }
}    

Answer 1

You have to include the extra props you need on the load:

clientContext.load(fileVersions, "Include(CreatedBy)");

Since you are using other props too, you'll need those in the include:

clientContext.load(fileVersions, "Include(CreatedBy,VersionLabel, Created, CheckInComment)");

You can reduce the size of the data returned from the query if you specify the load to only include the data you use:

clientContext.load(fileVersions, "Include(CreatedBy.LoginName,VersionLabel, Created, CheckInComment)");