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Emeka Elo-Chukwuma
Emeka Elo-Chukwuma

Posted on • Originally published at

Building password validation with strength meter in React with hooks


When building applications, you cannot avoid handling authentication and one of the ways to handle authentication is by receiving user data via a sign up or registration form and such forms contain passwords. You don't just want your users to use strong passwords that meet certain criteria but also visually inform them of how strong their passwords are during account creation.

In as much as password validation is done on the backend, the frontend validation helps guide the user in sending what the backend expects which ensures that your users as well as your systems are more secure. This article will show how to implement password validation from scratch(no library) as well as show the strength of the current password as the user types.


Here is a stackblitz demo of what we will be building.

Password validation criteria

For users to fulfill our "mysterious"🪄 validation criteria, their passwords must contain;

  • One uppercase character
  • One lowercase character
  • One numeric character
  • One special character
  • Eight or more characters

Or else,
You shall not pass

We will be using these regex patterns in the code snippet below to handle the validation:

  const atLeastOneUppercase = /[A-Z]/g; // capital letters from A to Z
  const atLeastOneLowercase = /[a-z]/g; // small letters from a to z
  const atLeastOneNumeric = /[0-9]/g; // numbers from 0 to 9
  const atLeastOneSpecialChar = /[#?!@$%^&*-]/g; // any of the special characters within the square brackets
  const eightCharsOrMore= /.{8,}/g; // eight characters or more
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Handling component state

State handling is inevitable and gladly a lot more easier with React hooks. Let's outline the states to track.

  const [meter, setMeter] = React.useState(false);
  const [password, setPassword] = React.useState('');
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  1. meter: This handles the visibility of the password strength meter.

  2. password: This takes care of the actual password the user types into the password field.

passwordTracker: Just a local variable that stores all the characters that pass a validation criteria as well as each criteria that they pass. It does so by storing the return value of the match() method(which is an array of the passing character(s)) to the property in the passwordTracker object that corresponds with the validation criteria.

    const passwordTracker = {
    uppercase: password.match(atLeastOneUppercase),
    lowercase: password.match(atLeastOneLowercase),
    number: password.match(atLeastOneNumeric),
    specialChar: password.match(atLeastOneSpecialChar),
    eightCharsOrGreater: password.match(eightCharsOrMore),
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Password input field and strength meter

This is a simple input field with functions to execute based on browser events. When a user focuses on the field, an anonymous function sets the meter state to true thereby displaying the password strength meter and validation criteria. The onChange event updates the state of the actual password as the user types.

          onFocus={() => setMeter(true)}
          onChange={(e) => setPassword(}
          placeholder="Enter password...pwetty please"
        {meter && (
            <div className="password-strength-meter"></div>
              {passwordStrength < 5 && 'Must contain '}
              {!passwordTracker.uppercase && 'uppercase, '}
              {!passwordTracker.lowercase && 'lowercase, '}
              {!passwordTracker.specialChar && 'special character, '}
              {!passwordTracker.number && 'number, '}
              {!passwordTracker.eightCharsOrGreater &&
                'eight characters or more'}
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In the validation criteria section, the negated value of a property is used to determine whether a criteria should be rendered or not. For example, if a password passes the atLeastOneUppercase regex, the value of the uppercase property is updated to a truthy value so that when negated(!), becomes false and does not render the 'uppercase, ' part any more. When falsy(null) it negates the value and becomes truthy which renders the 'uppercase, ' part letting users know that they still have to fulfill that criterion.

Lastly, we have the passwordStrength variable whose value is gotten from the number of truthy values in passwordTracker object.

const passwordStrength = Object.values(passwordTracker).filter(value => value).length;
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The idea is if 3 validation criteria are passed, the corresponding properties will have truthy values while the rest have falsy values (null). To know the number of criteria passed, we use the Object.values() method on the passwordTracker which returns an array of values. Then we filter for the truthy values and then obtain the length of the array with a .length.

passwordStrength is mainly use to determine the color and width of the password strength meter and also show or hide the 'Must contain ' part based on if all criteria are passed or not.

With CSS-in-JS, we are able to execute javaScript in our CSS styles using short circuit evaluation which assigns various colors to the background-color property. The width of the meter is given in percentage by multiplying the ratio of the number of passed criteria(which could be 1,2,3,4 or 5) to the total number of criteria(5) by 100

.password-strength-meter::before {
            content: "";
            background-color: ${
              ['red', 'orange', '#03a2cc', '#03a2cc', '#0ce052']
              [passwordStrength - 1] || ''
            height: 100%;
            width: ${(passwordStrength / 5) * 100}%;
            display: block;
            border-radius: 3px;
            transition: width 0.2s;
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It is more aesthetically pleasing and a better user experience to pinpoint the requirements a user needs to fulfill in order to navigate your app smoothly.

I really hope you've gained some insight on this article on how to implement password validation with password strength meter. I would love to know if there are any improvements that can be made on this implementation and also if you would prefer using a library over self implementation.

Feel free to share other implementations you have come across, suggestions, comments or questions.
Thanks for reading and happy coding.


If you would like to connect with me, I'm available on;

  • Discord: brunoelo#8120
  • Twitter: BrunoElo

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