Javascript 如何阻止一个先承诺后功能进入下一个后承诺功能？

我对承诺不熟悉，我觉得这应该是一件很简单的事情

如果变量返回true，我希望下面的代码首先停止

，然后停止

：

           if (groupCodes.length === 1) {
                // Get all does not populate the group object so it will just be the identifier as we require
                var groupIdentifier = groupCodes[0].group;

                GroupMember
                .nestedCreate({ groupId: groupIdentifier, type: groupCodes[0].type }, { })
                .$promise
                .then(function (group) {
                    var isUserAlreadyInGroup = _.includes(group, user._id);
                    if (isUserAlreadyInGroup) {
                        // If this variable returns true I would like to preent the below then function from running
                        notify.info('You have already joined ' + scope.groupCode);
                    }
                })
                .then(function () {
                    // Now that we have joined the group, we have permission
                    // to access the group data.
                    return Group
                        .getById({ groupId: groupIdentifier })
                        .$promise;
                })
           }

试试这个：

if (groupCodes.length === 1) {
    // Get all does not populate the group object so it will just be the identifier as we require
    var groupIdentifier = groupCodes[0].group;

    GroupMember
     .nestedCreate({ groupId: groupIdentifier, type: groupCodes[0].type }, { })
     .$promise
     .then(function (group) {
         var isUserAlreadyInGroup = _.includes(group, user._id);
         if (isUserAlreadyInGroup) {
             // If this variable returns true I would like to preent the below then function from running
             notify.info('You have already joined ' + scope.groupCode);
         }

         return isUserAlreadyInGroup;
     })
     .then(function (isUserAlreadyInGroup) {
         if (!isUserAlreadyInGroup) {
             // Now that we have joined the group, we have permission
             // to access the group data.
             return Group
              .getById({ groupId: groupIdentifier })
              .$promise;
             });
         })
     }

---

根据您对我的问题的回答，如果您正在使用的promise库没有提供您想要的方法，那么您可以始终让第二个

然后

成为一个单独的函数，从第一个

然后

函数有条件地调用该函数

var secondThen = function(groupIdentifier) {
  // Now that we have joined the group, we have permission
  // to access the group data.
  return Group
    .getById({
      groupId: groupIdentifier
    })
    .$promise;
};

首先，将第二个

定义为一个单独的函数

var secondThen = function(groupIdentifier) {
  // Now that we have joined the group, we have permission
  // to access the group data.
  return Group
    .getById({
      groupId: groupIdentifier
    })
    .$promise;
};

下面是您的示例中的
then
片段，使用我的建议

.then(function(group) {
    var isUserAlreadyInGroup = _.includes(group, user._id);
    if (isUserAlreadyInGroup) {
      notify.info('You have already joined ' + scope.groupCode);
    } else {
      // I'm not sure where `groupIdentifier` comes from, I assume you can figure that out, since you had it in your code
      secondThen(groupIdentifier);
    }
})

从第一个
然后是
方法返回一个值。在第二个
中询问该值，然后
确定是否应该继续。你用什么来兑现承诺？所问的问题实际上是一个骗局，但这种情况下的解决方案比复杂的承诺炼金术简单得多。。。。只需使用if-else语句合并这两个函数