Wordpress Ajax - returns 0 - ajax

Question

always returns 0, I have looked through other answers but nothing help.
Can anybody else help me find a solution?
plugin code:
function testOne(){
require_once plugin_dir_path( __FILE__ ) . "do.php";
}
add_shortcode( 'testOne' , 'testOne' );
od.php:
<?php
add_action( 'wp_ajax_myfun', 'myfun' );
add_action( 'wp_ajax_nopriv_myfun', 'myfun' );
function myfun() {
echo 'Test';
wp_die();
}
?>
<script>
$( document ).ready(function() {
$.ajax({
type:"POST",
url: ajaxurl,
data: {
action: "myfun",
},
success:function(data){
alert(data);
}
});
});
</script>
header.php in theme:
<script type='text/javascript'>
var ajaxurl = "<?php echo admin_url('admin-ajax.php'); ?>";
</script>

Answer 1

It seems that there is some issue with ajaxurl variable.
I suggest you to please create a separate javascript file for all code between script tag and than enqueue that script and localize it with ajaxurl.
Below is sample code for localizing :-
wp_register_script( 'my-cstm-script', 'script_url_path', array( 'jquery' ) );
wp_enqueue_script( 'my-cstm-script' );
wp_localize_script( 'my-cstm-script', 'MyCstmVar', array( 'ajaxurl' => admin_url( 'admin-ajax.php', ( is_ssl() ? 'https' : 'http' ) ), ) );
After this please in php file, which includes on that page, just add your function code and check whether this is working or not.
Let me know if you need further assistance.

Answer 2

#user3231235 your code is right only write your whole code out of your function which you would declare in plugin.

Answer 3

Try Below Code:
<script>
jQuery(document).ready(function() {
jQuery.ajax({
type: 'POST',
url: ajaxurl,
data: {
'action':'myfun',
},
success: function (data) {
alert(data);
}
});//end ajax
});
</script>
Put below ajax function in your theme's functions.php
add_action( 'wp_ajax_nopriv_myfun', 'myfun' );
add_action( 'wp_ajax_myfun', 'myfun' );
if( !function_exists('myfun') ):
function myfun(){
echo 'Test';
exit();
}
endif;
Hope this will Help!