获取SharePoint2010客户端OM/ECMAScript中的当前用户

您需要首先检索用户并加载web,而不是用户。

以下方法应该有效:

var currentcontext = new SP.ClientContext.get_current();
var currentweb = currentcontext.get_web();
currentcontext.load(currentweb);
var currentuser = currentweb.get_currentUser();
currentuser.retrieve();
currentcontext.load(currentweb);
var loginName = currentuser.get_loginName();

有关使用异步查询的更好示例,请参阅以下教程: SharePoint 2010 ECMAScript - How to know logged in user information

下面是executeQueryAsync的更完整示例:

SP.SOD.executeOrDelayUntilScriptLoaded(runMyCode, "SP.js");
function runMyCode() {
    var ctx = new SP.ClientContext.get_current();
    var web = ctx.get_web();
    ctx.load(web);
    var user = web.get_currentUser();
    user.retrieve();
    ctx.executeQueryAsync(
        function () {
                    //only in the success case you can work with user login
            doSomethingWithUserLogin(user.get_loginName());
        }, 
        function (data) {
            //notify the failure
    });
}