按 ID 获取列表项

SP.SOD.executeOrDelayUntilScriptLoaded(myFunction,"sp.js");

function myFunction(){
    var clientContext = new SP.ClientContext();
    var list = clientContext.get_web().get_lists().getByTitle("List Title");
    var item = list.getItemById(1); // get item with ID == 1
    clientContext.load(item);
    clientContext.executeQueryAsync(
        function(){ // onSuccess
            var title = item.get_item("Title");
            alert(title);
        },
        function(sender,args){ // onError
            alert(args.get_message());
        }
    );
}