Article: https://hwk.fr/blog/acf-creer-un-formulaire-de-connexion-inscription-en-ajax-grace-acf-form

wp-acf-form-ajax-frontend-script.js

/**
 *  ACF Form: Prevent default form submit
 */
jQuery(document).on('submit', '.acf-form', function(e) {
    e.preventDefault();
});

/**
 *  ACF Form: Init
 */
jQuery(document).ready(function($) {
    
    /** Check ACF */
    if(typeof acf === 'undefined')
        return;

    /** Add style for Datepicker */
    $(".hasDatepicker").addClass("form-control");
    
    /** Clean errors before checking validation again */
    acf.addAction('validation_begin', function($form) {
        $form.find('.acf-error-message').remove();
    });
    
    /** Add field errors */
    acf.addAction('invalid_field', function(field) {
        var $field = field.$el;
        $field.find('.acf-notice.-error').insertAfter($field.find('.acf-input-wrap'));
    });

    /** Make ACF Form use "formdata" instead of classic submission */
    acf.addAction('submit', function($form) {
        var formdata = new FormData($form[0]);
        
        $.ajax({
            url: window.location.href,
            type: 'post',
            data: formdata,
            cache: false,
            processData: false,
            contentType: false,
            success: function(response){
                
                // Form: Reset
                acf.validation.reset($form);
                
                if(!response.data)
                    return false;
                
                // Form: Invalid
                if(!response.success){
                    $form.prepend('<div class="acf-error-message -error">' + response.data.error + '</div>');
                    
                    $('html, body').animate({
                        scrollTop: $form.offset().top - 150
                    }, 500);
                    
                    return false;
                }

                // Form: Valid
                // Message
                if(response.data.data.message){
                    $form.prepend('<div class="acf-error-message -success">' + response.data.data.message + '</div>');
                    $('html, body').animate({
                        scrollTop: $form.offset().top - 150
                    }, 500);
                }
                
                // Redirect
                if(response.data.data.redirect)
                    window.location = response.data.data.redirect;
                
            }
        });
    });
    
});