How to use jsforce to post to opportunity chatter

Question

I am trying to use jsforce to post a message to the chatter section of a salesforce opportunity. I pieced the following together from watching how salesforce.com works, but it doesn't do what I want it to do. I am guessing on some of this. recordId is the opportunity number as pulled from the salesforce URL. I am using similar code to create tasks and upload files to an opportunity and that works fine. Does anyone have any ideas as to how to approach this? Thanks!

    conn.sobject('/feed-elements').create({
        feedElementType: "FeedItem",
        feedItemInput: {
            subjectId: recordId,
            body: {
                messageSegments: [
                    {
                        "type":"MarkupBegin",
                        "markupType":"Paragraph"
                    },
                    {
                        type: 'Text',
                        text: 'This is new comment #1'
                    },
                    {
                        "type":"MarkupEnd",
                        "markupType":"Paragraph"
                    }
                ]
            }
        }
    });

Answer 1

conn.sobject is for SOQL and DML using REST APIs.

Try using the chatter REST APIs as documented in jsforce docs

conn.chatter.resource('/feed-elements').create({
 body: {
      messageSegments: [
                {
                    "type":"MarkupBegin",
                    "markupType":"Paragraph"
                },
                {
                    type: 'Text',
                    text: 'This is new comment #1'
                },
                {
                    "type":"MarkupEnd",
                    "markupType":"Paragraph"
                }
            ]
  },
 feedElementType : 'FeedItem',
 subjectId: recordId
}, function(err, result) {
   if (err) { return console.error(err); }
     console.log("Id: " + result.id);
     console.log("URL: " + result.url);
     console.log("Body: " + result.body.messageSegments[0].text);
     console.log("Comments URL: " + 
     result.capabilities.comments.page.currentPageUrl);
 });