What is the best way to assign the result of a promise to a variable?

Question

What is the best way to assign the result of a promise to a variable?

My code includes an async function that retrieves a value

  async fetchUserName(environment: string, itemName: string, authToken: string): Promise<any> {
      let result = await this.obtainDeviceName(environment, itemName, authToken);
      return result;
  };

In another part of my code, I am invoking the aforementioned function as follows:

let productName;
const prod = this.fetchUserName(environment, itemName, authToken).then((response) => {
    productName = response;
    this.wait(300);
});

Even though the variable `productName` appears to be functioning correctly and displaying the response in my log, when I attempt to use `productName` outside of this particular block, I encounter an issue where it is undefined.

 promoDetails = { 
    name: productName,
    startDate: start,
    endDate: end
 };

I am trying to assign `productName` to the `name` field within the `promoDetails` object, but unfortunately, I cannot seem to get it working as intended.

If anyone could provide insight into what may be causing this issue, I would greatly appreciate it. Thank you.

javascript typescript promise async-await

Answer 1

Answer №1

If you want to set the value of promotion when receiving the response -

const prod = this.getUsername(env,skuName,token).then((resp) => {
    productN =  resp;
    promotion.name = resp
    this.wait(300);
});

As getUsername is an asynchronous function, you can use await to wait for the response before assigning to the promotion object.

(async() => {
  const resp = await this.getUsername(env,skuName,token);
  promotion = {
    name: resp,
    startDate: start,
    endDate: end
  } 
})();

--- Edit ---

const input = [
    {
        env: 'lorem',
        skuname: 'skuname1',
        token: 'dummy'
    }, 
    {
        env: 'lorem',
        skuname: 'skuname2',
        token: 'dummy'
    }
];

const getUserName = (username) => {
    return new Promise(resolve => {
        setTimeout(()=>resolve(username), 2000);
    });
};

(async () => {
    const resp = await Promise.all(input.map(({skuname}) => getUserName(skuname)));
    console.log(resp);
})();

// Or 

Promise.all(input.map(({skuname}) => getUserName(skuname)))
    .then(resp => {
        console.log(resp);
    });

Answer 2

If you want to set the value of promotion when receiving the response -

const prod = this.getUsername(env,skuName,token).then((resp) => {
    productN =  resp;
    promotion.name = resp
    this.wait(300);
});

As getUsername is an asynchronous function, you can use await to wait for the response before assigning to the promotion object.

(async() => {
  const resp = await this.getUsername(env,skuName,token);
  promotion = {
    name: resp,
    startDate: start,
    endDate: end
  } 
})();

--- Edit ---

const input = [
    {
        env: 'lorem',
        skuname: 'skuname1',
        token: 'dummy'
    }, 
    {
        env: 'lorem',
        skuname: 'skuname2',
        token: 'dummy'
    }
];

const getUserName = (username) => {
    return new Promise(resolve => {
        setTimeout(()=>resolve(username), 2000);
    });
};

(async () => {
    const resp = await Promise.all(input.map(({skuname}) => getUserName(skuname)));
    console.log(resp);
})();

// Or 

Promise.all(input.map(({skuname}) => getUserName(skuname)))
    .then(resp => {
        console.log(resp);
    });

Answer 3

Answer №2

attempt

let item = await this.fetchUserInfo(id,userName,key);
console.log(item);

Answer 4

attempt

let item = await this.fetchUserInfo(id,userName,key);
console.log(item);

Answer 5

Answer №3

Could you attempt this approach? Modify your getDeviceName function within the getUsername method;

getUsername(env:string, skuName: string, token:string): Promise<any> {
  return this.getDeviceName(env, skuName, token);
};
const productN = await this.getUsername(env, skuName, token);
console.log(productN);

I am uncertain why you are using the getUsername function when you can directly obtain the value of productN from getDeviceName.

For example

const productN = await this.getDeviceName(env, skuName, token);

If you need to perform any additional tasks within the getUsername method, you can make it return a promise.

getUsername(env:string, skuName: string, token:string): Promise<any> {
 return New Promise(async (resolve,reject)=>{
  try {
   let value =  await this.getDeviceName(env,skuName,token);
   ...
   //all other operations you wish to execute here 
   ...
   resolve(value);
  } catch (error) {
   reject(error)
  }
 }
};

const productN = await this.getUsername(env, skuName, token);
console.log(productN);

Note: I included a try catch block for error handling, feel free to disregard if unnecessary.

Answer 6

Could you attempt this approach? Modify your getDeviceName function within the getUsername method;

getUsername(env:string, skuName: string, token:string): Promise<any> {
  return this.getDeviceName(env, skuName, token);
};
const productN = await this.getUsername(env, skuName, token);
console.log(productN);

I am uncertain why you are using the getUsername function when you can directly obtain the value of productN from getDeviceName.

For example

const productN = await this.getDeviceName(env, skuName, token);

If you need to perform any additional tasks within the getUsername method, you can make it return a promise.

getUsername(env:string, skuName: string, token:string): Promise<any> {
 return New Promise(async (resolve,reject)=>{
  try {
   let value =  await this.getDeviceName(env,skuName,token);
   ...
   //all other operations you wish to execute here 
   ...
   resolve(value);
  } catch (error) {
   reject(error)
  }
 }
};

const productN = await this.getUsername(env, skuName, token);
console.log(productN);

Note: I included a try catch block for error handling, feel free to disregard if unnecessary.

What is the best way to assign the result of a promise to a variable?

Answer №1

Answer №2

Answer №3

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