understrap/inc/extras.php

<?php
/**
 * Custom functions that act independently of the theme templates.
 *
 * Eventually, some of the functionality here could be replaced by core features.
 *
 * @package understrap
 */
/**
 * Adds custom classes to the array of body classes.
 *
 * @param array $classes Classes for the body element.
 * @return array
 */

if ( ! function_exists ( 'understrap_body_classes' ) ) {
	function understrap_body_classes( $classes ) {
		// Adds a class of group-blog to blogs with more than 1 published author.
		if ( is_multi_author() ) {
			$classes[] = 'group-blog';
		}
		// Adds a class of hfeed to non-singular pages.
		if ( ! is_singular() ) {
			$classes[] = 'hfeed';
		}
		return $classes;
	}
}
add_filter( 'body_class', 'understrap_body_classes' );

// Removes tag class from the body_class array to avoid Bootstrap markup styling issues.

add_filter( 'body_class', 'adjust_body_class' );

if ( ! function_exists ( 'adjust_body_class' ) ) {
	function adjust_body_class( $classes ) {

	    foreach ( $classes as $key => $value ) {
	        if ( $value == 'tag' ) unset( $classes[ $key ] );
	    }

	    return $classes;

	}
}

// Filter custom logo with correct classes
add_filter('get_custom_logo','change_logo_class');

if ( ! function_exists ( 'change_logo_class' ) ) {
	function change_logo_class($html)
	{
		$html = str_replace('class="custom-logo"', 'class="img-responsive"', $html);
		$html = str_replace('class="custom-logo-link"', 'class="navbar-brand custom-logo-link"', $html);
		return $html;
	}
}