Replace price range handling default variation displayed price in Woocommerce 3

On our woocommerce website I am trying to update the displayed price based on the variations the customer selects from dropdown menus as shown here:

I used a php function that had been submitted in another answer by LoictheAztec:
Replace the Variable Price range by the chosen variation price in WooCommerce 3

add_action( 'woocommerce_before_single_product', 'move_variations_single_price', 1 );
function move_variations_single_price(){
    global $product, $post;

    if ( $product->is_type( 'variable' ) ) {
        // removing the variations price for variable products
        remove_action( 'woocommerce_single_product_summary', 'woocommerce_template_single_price', 10 );

        // Change location and inserting back the variations price
        add_action( 'woocommerce_single_product_summary', 'replace_variation_single_price', 10 );
    }
}

function replace_variation_single_price(){
    global $product;

    // Main Price
    $prices = array( $product->get_variation_price( 'min', true ), $product->get_variation_price( 'max', true ) );
    $price = $prices[0] !== $prices[1] ? sprintf( __( 'From: %1$s', 'woocommerce' ), wc_price( $prices[0] ) ) : wc_price( $prices[0] );

    // Sale Price
    $prices = array( $product->get_variation_regular_price( 'min', true ), $product->get_variation_regular_price( 'max', true ) );
    sort( $prices );
    $saleprice = $prices[0] !== $prices[1] ? sprintf( __( 'From: %1$s', 'woocommerce' ), wc_price( $prices[0] ) ) : wc_price( $prices[0] );

    if ( $price !== $saleprice && $product->is_on_sale() ) {
        $price = '<del>' . $saleprice . $product->get_price_suffix() . '</del> <ins>' . $price . $product->get_price_suffix() . '</ins>';
    }

    ?>
    <style>
        div.woocommerce-variation-price,
        div.woocommerce-variation-availability,
        div.hidden-variable-price {
            height: 0px !important;
            overflow:hidden;
            position:relative;
            line-height: 0px !important;
            font-size: 0% !important;
        }
    </style>
    <script>
    jQuery(document).ready(function($) {
        $('select').blur( function(){
            if( '' != $('input.variation_id').val() ){
                if($('p.availability'))
                    $('p.availability').remove();
                $('p.price').html($('div.woocommerce-variation-price > span.price').html()).append('<p class="availability">'+$('div.woocommerce-variation-availability').html()+'</p>');
                console.log($('input.variation_id').val());
            } else {
                $('p.price').html($('div.hidden-variable-price').html());
                if($('p.availability'))
                    $('p.availability').remove();
                console.log('NULL');
            }
        });
    });
    </script>
    <?php

    echo '<p class="price">'.$price.'</p>
    <div class="hidden-variable-price" >'.$price.'</div>';
}

However when a variation is selected it displays undefined underneath the From: $price as shown here:

Example of undefined error:

So if anyone could help me determine the cause of this error so that the price is now displayed and updated based on variations that have been selected it would be greatly appreciated.

Update 3

I have made some big changes and enhancements… This code version also solve the case when a variation is selected by default for a variable product (to get rid of that "undefined" bug…) and solved some other bugs in particular cases.

Note - The code might not work in some cases: For some themes or some plugins (like German Market for example) that make their own changes, using those hooks or changing the default html structure. In some cases your own customizations can be guilty.

Here is the new code:

// Utility function to get the default variation (if it exist)
function get_default_variation( $product ){
    $attributes_count = count($product->get_variation_attributes());
    $default_attributes = $product->get_default_attributes();
    // If no default variation exist we exit
    if( $attributes_count != count($default_attributes) )
        return false;

    // Loop through available variations
    foreach( $product->get_available_variations() as $variation ){
        $found = true;
        // Loop through variation attributes
        foreach( $variation['attributes'] as $key => $value ){
            $taxonomy = str_replace( 'attribute_', '', $key );
            // Searching for a matching variation as default
            if( isset($default_attributes[$taxonomy]) && $default_attributes[$taxonomy] != $value ){
                $found = false;
                break;
            }
        }
        // If we get the default variation
        if( $found ) {
            $default_variaton = $variation;
            break;
        }
        // If not we continue
        else {
            continue;
        }
    }
    return isset($default_variaton) ? $default_variaton : false;
}

add_action( 'woocommerce_before_single_product', 'move_variations_single_price', 1 );
function move_variations_single_price(){
    global $product, $post;

    if ( $product->is_type( 'variable' ) ) {
        // removing the variations price for variable products
        remove_action( 'woocommerce_single_product_summary', 'woocommerce_template_single_price', 10 );

        // Change location and inserting back the variations price
        add_action( 'woocommerce_single_product_summary', 'replace_variation_single_price', 10 );
    }
}

function replace_variation_single_price(){
    global $product;

    // Main Price
    $prices = array( $product->get_variation_price( 'min', true ), $product->get_variation_price( 'max', true ) );
    $active_price = $prices[0] !== $prices[1] ? sprintf( __( 'From: %1$s', 'woocommerce' ), wc_price( $prices[0] ) ) : wc_price( $prices[0] );

    // Sale Price
    $prices = array( $product->get_variation_regular_price( 'min', true ), $product->get_variation_regular_price( 'max', true ) );
    sort( $prices );
    $regular_price = $prices[0] !== $prices[1] ? sprintf( __( 'From: %1$s', 'woocommerce' ), wc_price( $prices[0] ) ) : wc_price( $prices[0] );

    if ( $active_price !== $regular_price && $product->is_on_sale() ) {
        $price = '<del>' . $regular_price . $product->get_price_suffix() . '</del> <ins>' . $active_price . $product->get_price_suffix() . '</ins>';
    } else {
        $price = $regular_price;
    }

    // When a default variation is set for the variable product
    if( get_default_variation( $product ) ) {
        $default_variaton = get_default_variation( $product );
        if( ! empty($default_variaton['price_html']) ){
            $price_html = $default_variaton['price_html'];
        } else {
            if ( ! $product->is_on_sale() )
                $price_html = $price = wc_price($default_variaton['display_price']);
            else
                $price_html = $price;
        }
        $availiability = $default_variaton['availability_html'];
    } else {
        $price_html = $price;
        $availiability = '';
    }
    // Styles ?>
    <style>
        div.woocommerce-variation-price,
        div.woocommerce-variation-availability,
        div.hidden-variable-price {
            height: 0px !important;
            overflow:hidden;
            position:relative;
            line-height: 0px !important;
            font-size: 0% !important;
        }
    </style>
    <?php // Jquery ?>
    <script>
    jQuery(document).ready(function($) {
        var a = 'div.wc-availability', p = 'p.price';

        $('select').blur( function(){
            if( '' != $('input.variation_id').val() ){
                if($(a).html() != '' ) $(a).html('');
                $(p).html($('div.woocommerce-variation-price > span.price').html());
                $(a).html($('div.woocommerce-variation-availability').html());
            } else {
                if($(a).html() != '' ) $(a).html('');
                $(p).html($('div.hidden-variable-price').html());
            }
        });
    });
    </script>
    <?php

    echo '<p class="price">'.$price_html.'</p>
    <div class="wc-availability">'.$availiability.'</div>
    <div class="hidden-variable-price" >'.$price.'</div>';
}

Code goes in function.php file of your active child theme (or active theme). Tested and works.