ReferenceError: _id is not defined - node.js

Question

Trying to pass in an _id to allow my comments to post to my front end React app. When I test express route in postman I don't get the comment . See screen shot below. When I try to post the comment I get the reference error _id id not defined.
Update:
The _id is fixed with id: data._id but I am not able to see my comments when I test in browser:
Here is backend express/node GalleryController.js
const mongoose = require('mongoose');
const Posts = mongoose.model('posts');
exports.PostGalleryInput = async (req, res) => {
console.log(req.body);
await new Posts({
body: req.body,
_id: req.params.id
}).save(async (err, data) => {
if (err) {
console.log('err:', err);
res.status(500).json({
message: 'Something went wrong, please try again later.'
});
} else {
res.status(200).json({
message: 'Post Created',
data,
id: _id
});
}
});
};
Here is Data Schema:
const mongoose = require('mongoose');
const PostSchema = new mongoose.Schema(
{
id: String,
title: String,
body: String,
name: String,
url: String,
comment: String
},
{
collection: 'posts'
}
);
module.exports = mongoose.model('posts', PostSchema);
Here is front end React component
import React, { useState, useEffect } from 'react';
import Container from 'react-bootstrap/Container';
import Card from 'react-bootstrap/Card';
import Button from 'react-bootstrap/Button';
import axios from 'axios';
import './css/sharewall.css';
const Cards = () => {
const [posts, setPosts] = useState([]);
const [comment, setComment] = useState('');
const loadPosts = async () => {
try {
let res = await axios.get(`http://localhost:5000/getall`);
setPosts(res.data.reverse());
} catch (error) {
console.log(error);
}
};
function saveComment(e, _id) {
e.preventDefault();
axios({
method: 'POST',
url: 'http://localhost:5000/postinput',
data: {
_id: _id,
comment: comment
}
})
.then((res) => {
loadPosts();
})
.catch((err) => {
console.log(err);
});
}
const loadComment = async () => {
try {
let res = await axios.post('http://localhost:5000/postinput');
setComment(res.data.comment._id);
console.log(res.data.comment._id);
} catch (error) {
console.log(error);
}
};
useEffect(() => {
loadPosts();
loadComment();
}, []);
return (
<div className="compoentclass">
<Container className="mt-5 ml-auto mr-auto">
<div className="text-center">
{posts.map(
(post) =>
post.url && (
<div key={post._id}>
<Card className="">
<Card.Img alt="" src={post.url} />
<Card.ImgOverlay className="overlay">
<Card.Title className="d-flex justify-content-center align-items-center">
<Card.Text className="cardStyle text-light">{post.body}</Card.Text>
</Card.Title>
</Card.ImgOverlay>
</Card>
<div>
<Card.Text>{post.comment}</Card.Text>
</div>
<textarea
className="comment text-center mt-3 mb-3"
onChange={(e) => setComment(e.target.value)}
name="comment"
type="text"
/>
<div className="d-flex justify-content-start mt-n3 mb-4">
<Button
className="shareButton"
variant="secondary"
onClick={(e) => saveComment(e, post._id)}
>
Comment
</Button>
</div>
</div>
)
)}
</div>
</Container>
</div>
);
};
export default Cards;