What is the process for transforming promises into async await syntax?

Question

What is the process for transforming promises into async await syntax?

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 functionality is part of my model designed to retrieve data from Mongodb. Implemented using express js. I'm exploring the possibility of refactoring this code to utilize async and await for achieving the same result as with promises.

Guidance on implementing this modification would be greatly appreciated.

javascript mongodb express async-await promise

Answer 1

Answer №1

Here is a solution for your login function:

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
   }
}

Creating another version of the login function will yield the following code snippet:

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');
   }
}

To use the updated login function, you can simply await (or use .then(), but it's recommended to use await) the result like this:

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

Remember to mark the caller function as async if you want to utilize the await operator.

Answer 2

Here is a solution for your login function:

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
   }
}

Creating another version of the login function will yield the following code snippet:

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');
   }
}

To use the updated login function, you can simply await (or use .then(), but it's recommended to use await) the result like this:

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

Remember to mark the caller function as async if you want to utilize the await operator.

What is the process for transforming promises into async await syntax?

Answer №1

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