// functions.php

add_action( 'user_profile_update_errors', 'validateProfileUpdate', 10, 3 );
add_filter( 'registration_errors', 'validateRegistration', 10, 3 );
add_action( 'validate_password_reset', 'validatePasswordReset', 10, 2 );

/**
 * validate profile update
 *
 * @author  Joe Sexton <joe.@webtipblog.com>
 * @param   WP_Error $errors
 * @param   boolean $update
 * @param   object $user raw user object not a WP_User
 */
public function validateProfileUpdate( WP_Error &$errors, $update, &$user ) {
    return validateComplexPassword( $errors );
}

/**
 * validate registration
 *
 * @author  Joe Sexton <joe.@webtipblog.com>
 * @param   WP_Error $errors
 * @param   string $sanitized_user_login
 * @param   string $user_email
 * @return  WP_Error
 */
function validateRegistration( WP_Error &$errors, $sanitized_user_login, $user_email ) {
    return validateComplexPassword( $errors );
}

/**
 * validate password reset
 *
 * @author  Joe Sexton <joe.@webtipblog.com>
 * @param   WP_Error $errors
 * @param   stdClass $userData
 * @return  WP_Error
 */
function validatePasswordReset( WP_Error &$errors, $userData ) {
    return validateComplexPassword( $errors );
}

/**
 * validate complex password
 *
 * @author  Joe Sexton <joe.@webtipblog.com>
 * @param   WP_Error $errors
 * @param   stdClass $userData
 * @return  WP_Error
 */
function validateComplexPassword( $errors ) {
    $password = ( isset( $_POST[ 'pass1' ] ) && trim( $_POST[ 'pass1' ] ) ) ? $_POST[ 'pass1' ] : null;

    // no password or already has password error
    if ( empty( $password ) || ( $errors->get_error_data( 'pass' ) ) )
        return $errors;

    // validate
    if ( ! isStrongPassword( $password ) )
        $errors->add( 'pass', '<strong>ERROR</strong>: Your password must contain at least 8 characters.' ); // your complex password error message

    return $errors;
}

/**
 * isStrongPassword
 *
 * @author  Joe Sexton <joe.@webtipblog.com>
 * @param   string $password
 * @return  boolean
 */
function isStrongPassword( $password ) {
    return strlen( $password ) >= 8; // your complex password algorithm
}

wp_enqueue_script( 'password-strength-meter' );

<form>
    <input type="password" name="password" />
    <input type="password" name="password_retyped" />
    <span id="password-strength"></span>
    <input type="submit" disabled="disabled" value="Submit" />
</form>

function checkPasswordStrength( $pass1,
                                $pass2,
                                $strengthResult,
                                $submitButton,
                                blacklistArray ) {
    var pass1 = $pass1.val();
    var pass2 = $pass2.val();

    // Reset the form & meter
    $submitButton.attr( 'disabled', 'disabled' );
    $strengthResult.removeClass( 'short bad good strong' );

    // Extend our blacklist array with those from the inputs & site data
    blacklistArray = blacklistArray.concat( wp.passwordStrength.userInputBlacklist() )

    // Get the password strength
    var strength = wp.passwordStrength.meter( pass1, blacklistArray, pass2 );

    // Add the strength meter results
    switch ( strength ) {

        case 2:
            $strengthResult.addClass( 'bad' ).html( pwsL10n.bad );
            break;

        case 3:
            $strengthResult.addClass( 'good' ).html( pwsL10n.good );
            break;

        case 4:
            $strengthResult.addClass( 'strong' ).html( pwsL10n.strong );
            break;

        case 5:
            $strengthResult.addClass( 'short' ).html( pwsL10n.mismatch );
            break;

        default:
            $strengthResult.addClass( 'short' ).html( pwsL10n.short );

    }

    // The meter function returns a result even if pass2 is empty,
    // enable only the submit button if the password is strong and
    // both passwords are filled up
    if ( 4 === strength && '' !== pass2.trim() ) {
        $submitButton.removeAttr( 'disabled' );
    }

    return strength;
}

jQuery( document ).ready( function( $ ) {
    // Binding to trigger checkPasswordStrength
    $( 'body' ).on( 'keyup', 'input[name=password1], input[name=password2]',
        function( event ) {
            checkPasswordStrength(
                $('input[name=password]'),         // First password field
                $('input[name=password_retyped]'), // Second password field
                $('#password-strength'),           // Strength meter
                $('input[type=submit]'),           // Submit button
                ['black', 'listed', 'word']        // Blacklisted words
            );
        }
    );
});

add_filter( 'gettext_with_context', 'wpse199813_change_password_indicatior', 10, 4 );

function wpse199813_change_password_indicatior($translations, $text, $context, $domain){

    if( $text == "Weak" && $context == "password strength")
        return "OK";

    return $translations;
}

add_filter('gettext', 'translate_text');
add_filter('ngettext', 'translate_text');

function translate_text($translated) {
$translated = str_ireplace('Very Weak', 'Bad', $translated);
$translated = str_ireplace('Weak', 'OK', $translated);

return $translated;
}

add_action( 'wp_enqueue_scripts', 'my_strength_meter_localize_script' );
function my_strength_meter_localize_script() {
    wp_localize_script( 'password-strength-meter', 'pwsL10n', array(
        'empty'    => __( 'But... it's empty!', 'theme-domain' ),
        'short'    => __( 'Too short!', 'theme-domain' ),
        'bad'      => __( 'Not even close!', 'theme-domain' ),
        'good'     => __( 'You are getting closer...', 'theme-domain' ),
        'strong'   => __( 'Now, that's a password!', 'theme-domain' ),
        'mismatch' => __( 'They are completely different, come on!', 'theme-domain' )
    ) );
}