validate data using map function

I would like to validate data using map.I would like to get the key name and check some conditions

const obj = {
    firstName: ['errorFirstName', 'msgFirstName'],
    lastName: ['errorLastName', 'msgLastName'],
    middleName: ['errorMiddleName', 'msgMiddleName'],
  }
  if (Object.keys(obj).includes(field)) {
 //I would like to pass here the object key length for each key :example if(this.firstName.length === 0)
    if(this[obj[key]].length === 0) {
      const [hasError, msg] = obj[field];
      this[hasError] = true;
      this[msg] = `${field} is required.`;
    }
  }

>Solution :

Simply use the key field to retrieve the value from your object:

const obj = {
    firstName: ['errorFirstName', 'msgFirstName'],
    lastName: ['errorLastName', 'msgLastName'],
    middleName: ['errorMiddleName', 'msgMiddleName'],
  }
  if (Object.keys(obj).includes(field)) {
    if (obj[field].length === 0) {
      // your logic here
      const [hasError, msg] = obj[field];
      this[hasError] = true;
      this[msg] = `${field} is required.`;
    }
  }