jQuery Ajax不发送

So I am doing

var title = $("#newcourse_title").val();
var description = $("#newcourse_description").val();
var link = $("#newcourse_link").val();
var image = $("#newcourse_imagelink").val();
$.ajax({
    url: "/courses/addcourse/",
    dataType: "json",
    type: "POST",
    data: {
        title: title,
        description: description,
        link: link,
        img_link: image
    },
    success: function(response){
        console.log(response);
    }
});

but my expressjs application dosent even receive the request, that makes me think that it is a problem with the ajax. It dosent give any errors either. Here is my HTML code:

<div class="newpost_form">
<form id="new_course_form">
    <input type="text" id="newcourse_title">


    <textarea id="newcourse_description"></textarea>

    <input type="text" id="newcourse_link">

    <input type="text" id="newcourse_imagelink">



    <input type="submit" class="button newpost_submit" value="Submit">

</form>

thanks in advance!

There are several ways but I guess this will work

 function trigger(){

    var title = $("#newcourse_title").val();
    var description = $("#newcourse_description").val();
    var link = $("#newcourse_link").val();
    var image = $("#newcourse_imagelink").val();
    $.ajax({
        url: "/courses/addcourse/",
        dataType: "json",
        type: "POST",
        data: {
            title: title,
            description: description,
            link: link,
            img_link: image
        },
        success: function(response){
            console.log(response);
        }
    });

    }
 <input type="button" onclick="trigger()" class="button newpost_submit" value="Submit">


$("form").on("submit",function(event){
    event.preventDefault();
    trigger();
})

<input type="submit" class="button newpost_submit" value="Submit">

Ajax dataType is json and I think you should serialize the postData to Json. You can use JSON.stringify;

var title = $("#newcourse_title").val();
var description = $("#newcourse_description").val();
var link = $("#newcourse_link").val();
var image = $("#newcourse_imagelink").val();
var postData = {
        title: title,
        description: description,
        link: link,
        img_link: image
    };
$.ajax({
    url: "/courses/addcourse/",
    dataType: "json",
    type: "POST",
    data: JSON.stringify(postData),
    success: function(response){
        console.log(response);
    }
});