Very basic JS password strength test

index.js

// example usage - feel free to edit the STRENGTH_CRITERIA in the Password class
const { Password } = require('./Password')

const password_strong = new Password('Password123');
const password_weak = new Password('password');
const password_very_weak = new Password('1234');

password_strong.getPasswordStrength();
// { result: 'pretty strong', weakness: [ [ 'spec_char_count' ] ] }

password_weak.getPasswordStrength();
// {
//   result: 'weak',
//   weakness: [ [ 'spec_char_count' ], [ 'capital_letter_count' ] ]
// }

password_very_weak.getPasswordStrength(); 
// {
//   result: 'very weak',
//   weakness: [
//     [ 'alpha_numeric_count' ],
//     [ 'spec_char_count' ],
//     [ 'capital_letter_count' ]
//   ]
// }

Password.js

class Password {

  constructor(password){
    this.password = password;
    this.getPassword = () => password

    this.STRENGTH_CRITERIA = {
      length: 8,
      alpha_numeric_count: 8,
      spec_char_count: 1,
      capital_letter_count: 1
    };

    this.spec_char_count = password.split('').filter(char => '!@#$^&%*()+=-[]/{}|:<>?,.'.split('').includes(char))
      .length;

    this.alpha_numeric_count = password
      .split('')
      .filter(char => !'!@#$^&%*()+=-[]/{}|:<>?,.'.split('').includes(char)).length;

    this.capital_letter_count = password
      .split('')
      .filter(char => !'!@#$^&%*()+=-[]/{}|:<>?,.0123456789'.split('').includes(char))
      .filter(char => char === char.toUpperCase()).length;
  }

  getPasswordStrength() {
    let passwordStrength = {
      result: null,
      weakness: []
    };
    Object.keys(this.STRENGTH_CRITERIA).forEach(key => {
      if (this[key] < this.STRENGTH_CRITERIA[key]) {
          passwordStrength = {
            ...passwordStrength,
            result: getResult([...passwordStrength.weakness, [key]]),
            weakness: [...passwordStrength.weakness, [key]]
          };
        }
    });

    function getResult(weakness){
      if (weakness.length == 2) {
        return 'weak';
      } else if (weakness.length >= 3) {
        return 'very weak';
      } else {
      return 'pretty strong';
      }
    }
    
    return passwordStrength;
  }

}

module.exports = {
  Password
}