<a onclick="show_trend()" >Trend</a>

function show_trend() {

    // This does the ajax request
    $.ajax({
        url: ajaxurl,
        data: {
            'action':'render_admin_charts_page',

        },
        success:function(data) {
            // This outputs the result of the ajax request
            console.log(data);
        },
        error: function(errorThrown){
            console.log(errorThrown);
        }
    });
}

function render_admin_charts_page() {
    ?>
    <div class="wrap">
        <div class="em-bookings-events">
            <h2><?php esc_html_e('Event Booking Report','dbem'); ?></h2>
            <?php em_bookings_events_table(); ?>

        </div>
    </div>
    <?php
}

add_action( 'wp_ajax_render_admin_charts_page', 'yourfunction' );

function yourfunction() { ?>
    <div class="wrap">
        <div class="em-bookings-events">
            <h2><?php esc_html_e('Event Booking Report','dbem'); ?></h2>
            <?php em_bookings_events_table(); ?>
        </div>
    </div>
<?php   // Handle request then generate response using WP_Ajax_Response
}

jQuery.post(
    ajaxurl,
    {
        'action': 'render_admin_charts_page',
    },
    function(response){
        alert('The server responded: ' + response);
    }
);

add_action( 'wp_ajax_render_admin_charts_page', 'yourfunction' );

function yourfunction() { ?>
    <div class="wrap">
        <div class="em-bookings-events">
            <h2><?php esc_html_e('Event Booking Report','dbem'); ?></h2>
            <?php em_bookings_events_table(); ?>
        </div>
    </div>
<?php   // Handle request then generate response using WP_Ajax_Response
}

jQuery.ajax({
    url: fav_url ,  // path of that file
    type: 'GET',
    timeout: 20000,
    error: function(){
        alert("Error loading user's attending event.");
    },
    success: function(html){}
})