How can I get a userid with jQuery in SharePoint 2010?

Question

I'm writing a custom form with HTML and jQuery so that I can then insert the captured information into a list, but I can't use the SPServices library. When I build the list using InfoPath, it ended up being too slow for my client, so I decided to custom code it. Some of the fields are people, so I need to get the numeric userid of the person that's entered. The "GetUserProfileByName" service does not return the userid and the "ResolvePrincipals" service returns the wrong userid. How can I get the correct userid?

Here's my code:

<script type="text/javascript">
function GetUserInfo(Username, objAccountName, objUserID, objEmail, objErrorPlaceholder) {
    objErrorPlaceholder.text("");
    if(Username.length == 0){
        objEmail.val("");
    }
    else{
        var profileURL = "http://<domain>/_vti_bin/People.asmx";
        var soapEnv = "<soap:Envelope xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xmlns:xsd='http://www.w3.org/2001/XMLSchema' xmlns:soap='http://schemas.xmlsoap.org/soap/envelope/'> \
            <soap:Body> \
                <ResolvePrincipals xmlns='http://schemas.microsoft.com/sharepoint/soap/'> \
                    <principalKeys> \
                        <string>" + Username + "</string> \
                    </principalKeys> \
                    <principalType>User</principalType> \
                    <addToUserInfoList>1</addToUserInfoList> \
                </ResolvePrincipals>\
            </soap:Body> \
        </soap:Envelope>";
        $.ajax({
            url: profileURL,
            type: "POST",
            dataType: "xml",
            data: soapEnv,
            complete: function(xData){
                console.log($(xData.responseXML).find('*').html()); // DEBUGGING
                $(xData.responseXML).find("ResolvePrincipalsResponse").each(function() {
                    if($(this).find("IsResolved").text() == 'true'){
                        objUserID.val($(this).find("UserInfoID").text());
                        objAccountName.val($(this).find("AccountName").text());
                        objEmail.val($(this).find("Email").text());
                    }
                    else{
                        objErrorPlaceholder.text("This user could not be found, please enter the username or email address.");
                    }
                });
            },
            error: function(xData){
                objErrorPlaceholder.text("This user could not be found, please enter the username or email address.");
            },
            contentType: "text/xml; charset=\"utf-8\""
            });
    }
}

$(document).ready(function(){
    $('input[name=POCUsername]').change(function(){
        GetUserInfo($(this).val(), $('input[name=POCAccountName]'), $('input[name=POCID]'), $('input[name=POCEmail]'), $('span[name=POCUsernameError]'));
    });
    $('a[name=submit]').click(function(){
        // Submit data
        var ListName = 'MyList';
        var SiteUrl = '/sites/MySite/';
        var fieldNames = 'POC,POCEmail'.split(',');
            var fieldValues = new Array($('input[name=POCID]').val(),
                    $('input[name=POCEmail]').val()
                );
        createListItem(ListName, SiteUrl, fieldNames, fieldValues);
    });
});

/* Modified from: http://msdn.microsoft.com/en-us/library/office/hh185011(v=office.14).aspx */

function createListItem(ListName, SiteUrl, fieldNames, fieldValues) {
    var clientContext = new SP.ClientContext(SiteUrl);
    var oList = clientContext.get_web().get_lists().getByTitle(ListName);

    var itemCreateInfo = new SP.ListItemCreationInformation();
    this.oListItem = oList.addItem(itemCreateInfo);

    for(i=0; i<fieldNames.length; i++){
    oListItem.set_item(fieldNames[i], fieldValues[i]);}

    oListItem.update();

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

</script>

<span name="POCUsernameError"></span>
<span class="fieldTitle">POC Username</span>
<input type="text" name="POCUsername" />
<input type="hidden" name="POCAccountName" />
<input type="hidden" name="POCID" />
<span class="fieldTitle">POC Email</span>
<input type="text" name="POCEmail" />
<a href="javascript:void(0);" name="submit">Submit</a>

Answer 1

You can get check the link for getting user info(ID, First Name, Last Name, Email, Username, Name) by User login Name. https://sharepoint.stackexchange.com/a/146788/40602

Use following way to set people or group field in javascript

var user = User_ID + ';#' + User_Name;
listItem.set_item(fieldName, users); 
listItem.update();

Answer 2

ExecuteOrDelayUntilScriptLoaded(init,'sp.js');
var currentUser;
function init(){
    this.clientContext = new SP.ClientContext.get_current();
    this.oWeb = clientContext.get_web();
    currentUser = this.oWeb.get_currentUser();
    this.clientContext.load(currentUser);
    this.clientContext.executeQueryAsync(Function.createDelegate(this,this.onQuerySucceeded), Function.createDelegate(this,this.onQueryFailed));
}

function onQuerySucceeded() {
  userid = currentUser.get_id();
  alert(userid);
   }

Answer 3

@Yayati had a very helpful response, but I had to use "item.get_item('ID')" instead of item.ID in order to get it working for me. Here's my code:

function getUserInfo(AccountName) {
    var clientContext = new SP.ClientContext.get_current();
    var userInfoList = clientContext.get_web().get_siteUserInfoList();
    var query = new SP.CamlQuery();
    query.set_viewXml("<View><Query><Where><Eq><FieldRef Name='Name' /><Value Type='Text'>" + AccountName + "</Value></Eq></Where></Query><RowLimit>1</RowLimit></View>");
    items = userInfoList.getItems(query);
    clientContext.load(items, 'Include(Department,ID,EMail,Name,UserName,WorkPhone)');
    clientContext.executeQueryAsync(function(){
            if(items.get_count() > 0){
                item = items.itemAt(0);
                console.log(item.get_item('ID'));
            }
            else{
                console.log('User not found');
            }
        }, function(){console.log('Error');});
}