ajax请求从nodejs中的表单发布未定义的数据

Question

I am trying to make a comment form which adds a comment in array of blog schema but when I am using ajax it is giving undefined below the places where I have console log and when I am using simple post request it is working fine. I am using mongoose, nodejs , express, jquery ajax my script is as follows

var frm = $('#commentForm');

frm.submit(function (e) {
    e.preventDefault();
    console.log('clicked');
    $.ajax({
        type: 'POST',
        url: "/blog/addComment",
        contentType: "application/json; charset=utf-8",
        dataType: 'json'
        })
        .done(function(data) {
            addNewComment(data);
        })
        .fail(function() {
            console.log("Ajax failed to fetch data");
        });
});

function addNewComment(data){
    console.log(data);
}

my routes is as follows

//add comments
router.post('/addComment',function(req,res,next){
    console.log(req.body.comment+" "+ req.body.userId+" "+req.body.postId);
    var newComment = {
        'text': req.body.comment,
        'author': req.body.userId
    }
    Post.addComment(req.body.postId, newComment, function(err,comment){
        if(err) throw err;
        console.log(comment);
        res.send(comment);
    });
});

and my mongoose schema is

//add comments
module.exports.addComment = function( postId, newComment, callback){
    var query = { '_id': postId};
    console.log('postid: '+postId+"  newcomment: "+newComment.text+ " "+newComment.author);
    Post.findOneAndUpdate( query, { $push:{'comments': newComment} }, {new:true} , callback);
}

Answer 1

That's because data is not defined in ajax call , use following provide the frm is the actallu form or use use data : form name.serialize()

var frm = $('#commentForm');
frm.submit(function (e) {
e.preventDefault();
console.log('clicked');
$.ajax({
    data : $(this).serialize(),
    type: 'POST',
    url: "/blog/addComment",
    contentType: "application/json; charset=utf-8",
    dataType: 'json'
    })
    .done(function(data) {
        addNewComment(data);
    })
    .fail(function() {
        console.log("Ajax failed to fetch data");
    });
});