WooCommerce: How to retain checkout info when client leaves then comes back?

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The code below is working, but only if data is submitted!

The only possible ways are javascript/jQuery form event detection on checkout fields and worpress Ajax:

• Using ajax connected to some session transients function (as in code below).
• Using (javascript) web Storage: localStorage, sessionStorage…

I have found some real interesting code in this thread that is using sessions transients to store checkout data.

// this function sets the checkout form data as session transients whenever the checkout page validatesfunction set_persitent_checkout ( $a ) {    $arr = array();    foreach ( $a as $key => $value )        if ( ! empty($value) )            $arr[$key] = $value;    WC()->session->set( 'form_data', $arr );    return $a;}add_action( 'woocommerce_after_checkout_validation', 'set_persitent_checkout' );// this function hooks into woocommerce_checkout_get_value to substitute standard values with session values if presentfunction get_persistent_checkout ( $value, $index ) {    $data = WC()->session->get('form_data');    if ( ! $data || empty($data[$index]) )        return $value;    return is_bool($data[$index]) ? (int) $data[$index] : $data[$index];}add_filter( 'woocommerce_checkout_get_value', 'get_persistent_checkout', 10, 2 );// This is a fix for the ship_to_different_address field which gets it value differently if there is no POST data on the checkoutfunction get_persitent_ship_to_different ( $value ) {    $data = WC()->session->get('form_data');    if ( ! $data || empty($data['ship_to_different_address']) )        return $value;    return is_bool($data['ship_to_different_address']) ? (int) $data['ship_to_different_address'] : $data['ship_to_different_address'];}add_action( 'woocommerce_ship_to_different_address_checked', 'get_persitent_ship_to_different' );

Add this code to the functions.php file located in your active child theme or theme.

Explanations from the author:

1. Save the form data:

The first function set_persitent_checkout hooks into woocommerce_after_checkout_validation.

Whenever that hook is fired, any current form data is saved as a WordPress transient via the WC_Session_Handler class (which was recently updated in version 2.5 to be a lot more efficient).

2. Check the saved data on reload:

Next we hook woocommerce_checkout_get_value with get_persitent_checkout. As the name suggests, here we check the session transients and return any matches for the current field if found.

3. Make ship_to_different_address work:

The only difficult was the ship_to_different_address field, which gets its value through a different method.

To get around this the final function was added. This works exactly the same as the previous function, but hooks into woocommerce_ship_to_different_address_checked.

There you have it. It would be nice if the data was saved after every field update on checkout, but the woocommerce_after_checkout_validation hook fires enough to capture the data at all the important points.

https://github.com/kugaevsky/jquery-phoenix/ seems to be the perfect answer to this problem.

Functions.php snipped posted by LoicTheAztec didn't work for me.

I found this plugin which remembers everything I type or select in Woocommerce checkout, including shipping fields and my custom additions to the template:

Save Abandoned Carts – WooCommerce Live Checkout Field Capture

Account passwords, if creating during checkout, are naturally not remembered.