WordPress Ajax Not Working ( Custom Admin page)

Question

I tried to do a small thing using Ajax. I just try to replace a div.

This is what I have done so far.

I created a admin menu using add_menu_page.

Then I add a form to that page with a text field. I just need to replace a div when click the submit button. But it did not works. When I check console in browser it says Uncaught TypeError: Cannot read property 'ajax' of undefined

---

function myajaxfunction() {
    $.ajax({ //ajax request
        url: ajaxurl,
        data: {
            'action':'rs_like_request',
            'post_type' : $('#post_type').val() // value of text box having id "post_type"

        },
        success:function(data) {  //result
         $(".showdiv").html(data); //showdiv is the class of the div where we want to show the results
        },
        error: function(errorThrown){
            console.log(errorThrown);
        }
    });  

}

---

<form action="" method="post">
    <label>Write post type : </label>
    <input type="text" name="post_type" id="post_type" value=""/>
    <input type="button" value="Show Post Titles" onclick="myajaxfunction()"/>

    <div class="showdiv"></div>

</form>

---

function rs_like_count() {

    if ( isset($_REQUEST) ) {   // $_REQUEST is having all the data sent using ajax
        $post_type= $_REQUEST['post_type'];
        echo $post_type;

}
 die();
}
add_action( 'wp_ajax_rs_like_request', 'rs_like_count' );

Answer 1

Uncaught TypeError: Cannot read property 'ajax' of undefined

@Sasa1234, it happen cause your jQuery is undefined. Please take a look @EAMann answer. So, your JS code should like this:

function myajaxfunction() {
    if ( undefined !== window.jQuery ) {
        jQuery.ajax({ //ajax request
            url: ajaxurl,
            data: {
                'action':'rs_like_request',
                'post_type' : jQuery('#post_type').val() // value of text box having id "post_type"

            },
            success:function(data) {  //result
             jQuery(".showdiv").html(data); //showdiv is the class of the div where we want to show the results
            },
            error: function(errorThrown){
                console.log(errorThrown);
            }
        });  
    }
}