How to retrieve a ListItem using the Javascript Client Object Model?

Question

Right now I am using this method:

function getWebProperties(id) {
    var ctx = new SP.ClientContext.get_current();
    this.website = ctx.get_web();
    this.listCollection = website.get_lists();
    this.oList = listCollection.getByTitle('NavStructure');
    this.oItem = oList.getItemById(id);
    ctx.load(oItem, 'Include(Id, DisplayName)');
    ctx.executeQueryAsync(Function.createDelegate(this, this.onSuccess), Function.createDelegate(this, this.onFail));
}

function onSuccess(sender, args) {
        alert("Title: " + oItem.get_displayName() + " ID: " + oItem.get_id());
}

function onFail(sender, args) {
        alert('failed to get list. Error:' + args.get_message());
}

But it keeps erroring out (through the onFail method) with:

failed to get list. Error:Invalid request

I also changed this line:

ctx.load(oItem, 'Include(Id, DisplayName)');

to

ctx.load(oItem);

And it errored out (in the browser. never fired the onFail method) with:

uncaught exception: [Exception... "'Error: The property or field has not been initialized. It has not been requested or the request has not been executed. It may need to be explicitly requested.' when calling method: [nsIDOMEventListener::handleEvent]" nsresult: "0x8057001c (NS_ERROR_XPC_JS_THREW_JS_OBJECT)" location: "JS frame :: resource://firebug_rjs/net/spy.js :: callPageHandler :: line 796" data: no]

Can anyone see what I am doing wrong here?

Answer 1

Use ctx.load(oItem);

Then get the columns data using oItem.get_item('Title') OR oItem.get_item('ID')

I will try using ctx.load(oItem, 'Include(Id, DisplayName)'); and udpate the results in comments.

Hope this helps.

Answer 2

With lookup column and no 'Include' declaration.

var oItem ='';
function retrieveWebSite() {
    SP.SOD.executeFunc('sp.js', 'SP.ClientContext', function(){
        var clientContext = new SP.ClientContext.get_current();
        this.oWebsite = clientContext.get_web();
        clientContext.load(this.oWebsite);

        var lstObject = oWebsite.get_lists().getByTitle('Listname');
        oItem = lstObject.getItemById(5);
        clientContext.load(oItem);

        clientContext.executeQueryAsync(
            Function.createDelegate(this, this.onQuerySucceeded), 
            Function.createDelegate(this, this.onQueryFailed)       
        );
    });
}

function onQuerySucceeded(sender, args) {
    var look  = oItem.get_item('LookupColumnName').get_lookupValue();
    var title = oItem.get_item('Title');
    var id = oItem.get_id();
    alert("Loook up column value: "+look);
    alert("Title column: "+title);
    alert("Id column value: "+id);
}

function onQueryFailed(sender, args) {
    alert('Request failed. ' + args.get_message() + 
        '\n' + args.get_stackTrace());
}