<p>I'm using mongoose to create a new member entry in the database after checking if the member already exists in the database. I need to return a response if the member already exists, otherwise continue inserting the new member. Here is the code: </p> <pre class="brush:php;toolbar:false;">createNewMember = (req, res, next) => { Member.findOne({email: email}).exec() .then((members) => { if(members == null || members.length==0) { //Create new member object return newMember.save() // 1 --> return promise } else { res.status(409).json({message: "Member already exists"}) // 2 --> I want to return } }) .then((result) => { if(res.statusCode === 409) return res; // 3 --> I added this hack to solve the problem return res.status(201).json({message: "Member has been created"}); // 4 --> then block of newMember.save() }) .catch(err => { // Handle the error and return an error response })</pre> <p>What I want is that if the process reaches point 2, the promise chain is broken, but the second then block is still called. Point 3 is a check I added to prevent the second then block from being executed, but I don't think this is the best way to handle it. I believe this is a common scenario, is there a better way? </p>

Member.findOne({email: email}).exec()

    // DB layer
    .then((members) => {

         // 如果成员不存在，则开始保存并返回promise
         if(members == null || members.length==0) {
              // 创建newMember对象
              return newMember.save()   // 1 --> 返回promise
         } 

         // 如果成员存在，则返回undefined
         else {
             return;
         }
     })

     // Response Layer
     .then((newMember) => {
         let statusCode;
         let message;

         // 在.save()成功时，promise解析为新成员
         if(newMember) {
           statusCode = 201;
           message = "成员已创建";
         }

         // 如果我们在第一个.then()中返回了undefined，我们会到达这里
         else {
           statusCode = 409;
           message = "成员已存在";
         }

         return res.status(statusCode).json({message});
     })
     .catch(err => {
          // 处理错误并返回错误响应
     })