Check for empty object and return boolean

Question

I have a AddContactForm form that allows the user to add contacts.

When the user fills in the conactNumber- onBlur it checks if this conactNumber already exists.

How can I make The CheckIfContactExists function returns either true or false instead of the promise object?

Please note that I can't change the returned value from the api, it only return a contact object.

export default class AddContactForm extends Component {
  state = {
   ...
  };

  checkContact = () => {
    const { contactNumber } = this.state.newContactInfo;
    CheckIfContactExists(contactNumber); //return promise
  };

 render() {
   ...
    return (  
       ...
   );
  }
}

const CheckIfContactExists = async searchString => {
  const { data: contactsInfo } = await axios.get(`api/Contacts/SearchContact?contactNum=${searchString}`);
};

you can't, that's the thing with asynchronous calls they return promise, you can make it so promise resovles into boolean, but it will still be a promise — Krzysztof Krzeszewski
– Krzysztof Krzeszewski, Commented Feb 17, 2019 at 18:51

Tholle · Accepted Answer · 2019-02-17 19:22:40Z

1

You can't make it return just a boolean since it's an asynchronous operation. You could make the checkContact function async as well and await it.

Example

export default class AddContactForm extends Component {
  state = {
   // ...
  };

  checkContact = async () => {
    const { contactNumber } = this.state.newContactInfo;
    const contactInfo = await CheckIfContactExists(contactNumber);

    this.setState({
      contactNumberTaken: Object.keys(contactInfo).length !== 0
    });
  };

  render() {
    // ...
  }
}

edited Feb 17, 2019 at 19:22

answered Feb 17, 2019 at 18:56

Tholle

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2 Comments

user3378165 Over a year ago

Thank you for your answer, but Boolean(contactsInfo) will always result true, An object that doesn't have any properties assigned is not considered "empty".

Tholle Over a year ago

@user3378165 That's true. I updated the answer with a check to see if it's an empty object that was returned.

Shubham Khatri · Accepted Answer · 2019-02-18 05:38:05Z

1

Make use of async await in checkContact just like you did for CheckIfContactExists. Also return the boolean result from CheckIfContactExits method

export default class AddContactForm extends Component {
  state = {
   ...
  };

  checkContact = async () => {
    const { contactNumber } = this.state.newContactInfo;
    try {
      const res = await CheckIfContactExists(contactNumber); 
      return res;
    } catch (e) {
       console.log('Error', error);
    }
  };

 render() {
   ...
    return (  
       ...
   );
  }
}

const CheckIfContactExists = async searchString => {
  const { data: contactsInfo } = await axios.get(`api/Contacts/SearchContact?contactNum=${searchString}`);
  if (Object.keys(contactsInfo).length > 0) {
     return true;
  } else {
      return false;
  }
};

edited Feb 18, 2019 at 5:38

answered Feb 17, 2019 at 18:55

Shubham Khatri

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2 Comments

user3378165 Over a year ago

Thank you for your answer, but if (contactsInfo) will always result true, An object that doesn't have any properties assigned is not considered "empty".

Shubham Khatri Over a year ago

In that case you could simply check for size of object keys. My assumption when I wrote the answer was that the contactsInfo is returned undefined or null if not found

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