SharePoint JavaScript 更新用户与组字段

最近，需要更新列表字段，字段的类型是用户和组，so写了这么一段代码

复制代码
function updateUserField(){
var ctx = new SP.ClientContext.get_current();
var list = ctx.get_web().get_lists().getByTitle('My List');
var item = list.getItemById(1);//Item Id

var assignedToVal = new SP.FieldUserValue();
assignedToVal.set_lookupId(12);//User Id in the site collection
item.set_item("AssignedTo",assignedToVal);//AssignedTo is a column name
item.update();

ctx.executeQueryAsync(
function() {
console.log('Updated');
},
function(sender,args) {
console.log('An error occurred:' + args.get_message());
}
);
}
ExecuteOrDelayUntilScriptLoaded(updateUserField, "sp.js");