SharePoint Online Rest API创建新项目多选选择字段

我有一个SharePoint列表，其中包含一个多选选择字段(复选框).我正在使用HTML/JQuery/AJAX.我试图创建一个新的列表项，但我坚持添加多选选择字段的值.这是我的代码:

I have a SharePoint list with a multi-select choice field (checkboxes). I am using HTML/JQuery/AJAX. I am trying to create a new list item, but I'm stuck on adding the values of the multi-select choice field. Here is my code:

  
var eff = []; 
if ($('input[name="chkA"]').is(':checked')) {
        eff.push('"A"');
    }

    if ($('input[name="chkB"]').is(':checked')) {
        eff.push('"B"');
    }

    if ($('input[name="chkC"]').is(':checked')) {
        eff.push('"C"');
    }

    if ($('input[name="chkD"]').is(':checked')) {
        eff.push('"D"');
    }
var Effected = '{"__metadata":{"type":"Collection(Edm.String)"},"results":['+ eff.join(',') +']}';

$.ajax  
        ({  
        url: _spPageContextInfo.webAbsoluteUrl + "/_api/web/lists/GetByTitle('ListName')/items",  
        type: "POST",  
        data: JSON.stringify  
        ({  
            __metadata:  
            {  
                type: "SP.Data.InternalNameListItem"  
            },  
            Title: title,

Effected: Effected

        }),  
        headers:  
        {  
            "Accept": "application/json;odata=verbose",  
            "Content-Type": "application/json;odata=verbose",  
            "X-RequestDigest": $("#__REQUESTDIGEST").val(),  
            "X-HTTP-Method": "POST"  
        },  
        success: function(data, status, xhr)  
        {  
alert("Success!");
        },  
        error: function(xhr, status, error)  
        {  
alert("Failed!");
        }  
    });  

我在做什么错了?