如何将承诺转换为异步等待

Question

login() {
    return new Promise((resolve, reject) => {
        userCollection.findOne({email: this.data.email}).then((myUser)=>{
            if (myUser && myUser.password == this.data.password) {
                resolve("Congrats! Successfully logged in");
            } else{
                reject("Login failed");
            }
        }).catch(()=>{
            reject("Please try again later")
        })
    })
}

This is my model and I can use it to find data from Mongodb . I'm using express js. But, I want to know how I can use async await to do exactly the same thing that the above promise does. I mean, I would like to convert this code to async await way.

Any assistance would be highly appreciated.

Answer 1

This should suffice:

async function login() {
   try {
      const user = await userCollection.findOne({ email: this.data.email });

      if (user && user.password === this.data.password) {
         // handle valid user
      }
      else {
         // handle not found user or password mismatch
      }
   }
   catch (error) {
      // handle or rethrow error
   }
}

Duplicating your case will result in:

async function login() {
   try {
      const user = await userCollection.findOne({ email: this.data.email });

      if (user && user.password === this.data.password) {
         return 'Congrats! Successfully logged in';
      }
      else {         
         throw new Error('Login failed');
      }
   }
   catch (error) {
      throw new Error('Please try again later');
   }
}

Then in your caller code you can await (or .then() it, but prefer await ) the result of login:

try {
   const loginResult = await login();
}
catch(error) {
   // handle error
}

Note that in doing so, you will once again need to mark the caller function as async for you to be able to use the await operator.