如何在此 node.js 应用程序的警报中获取我的 err.message？

Question

I have a PUT in a REST API that should display an error message that says "upvoted already" if the vote_score is 1 (that is, they voted already), but instead I get a generic "internal server error" message in alert which is not good UX. That's always what the error will say with what I have tried so far.

How can I get my error message to display as "upvoted already"? Or for that matter, how can I get any error message to show up with a message? I hope I have provided enough information with the API code followed with the front-end code.

What I have tried thus far is trying different things like res.status(200).json({ error: err.toString() }); and next(err) .

Hopefully something simple, I am hoping for a ELI5 type answer because I am a beginner and my error-handling game is weak. Thanks.

const db = require('../db');
const express = require('express');
const debug = require('debug')('app:api:vote');
const Joi = require('joi');
const auth = require('../middleware/auth');
const admin = require('../middleware/admin');

const { required } = require('joi');
const router = express.Router();
router.use(express.urlencoded({ extended: false }));
router.use(express.json());

// general error handler
const sendError = (err, res) => {
  debug(err);
  if (err.isJoi) {
    res.json({ error: err.details.map((x) => x.message + '.').join('\n') });
  } else {
    res.json({ error: err.message });
  }
};
router.put('/upvote/:emojiId/', auth, async (req, res, next) => {
  try {
    const schema = Joi.object({
      emoji_id: Joi.number().required(),
      user_id: Joi.number().required(),
      vote_score: Joi.number(),
    });
    const vote = await schema.validateAsync({
      emoji_id: req.params.emojiId,
      user_id: req.user.user_id,
      vote_score: 1,
    });


    if (!(await db.findVoteByUser(vote.emoji_id, vote.user_id))) {
      const upvote = await db.upvote(vote);
    } else if ((await db.findVoteByUser(vote.emoji_id, vote.user_id)) == 1) {
      throw new Error('Upvoted already');
    }

    const upvoteScore = await db.getJustUpvotesForEmoji(vote.emoji_id);
    res.json(upvoteScore);

  } catch (err) {
    res.status(500).json({ error: err.toString() });
  }
});

module.exports = router;

And the front-end...

  $(document).on('click', '.upvote-emoji-button', (evt) => {
    const button = $(evt.currentTarget);
    const emoji_id = button.data('id');
    $.ajax({
      method: 'PUT',
      url: `/api/vote/upvote/${emoji_id}`,
      data: emoji_id,
      dataType: 'json',
    })
      .done((res) => {
        if (res.error) {
          bootbox.alert(res.error);
        } else {
          // $('#search-emoji-form').trigger('submit');
          button.addClass('btn-danger').removeClass('btn-primary');
          button.parent().next().next().html(res.upvotes);
          button.parent().next().next().next().next().html(res.vote_count);
          button.parent().next().next().next().next().next().html(res.total_score);
        }
      })
      .fail((xhr, textStatus, err) => {
        bootbox.alert(err);   
      });
  });

Answer 1

try to replace

res.status(500).json({ error: err.toString() });

with

res.status(400).send(err.toString());

Documentation

Answer 2

Here is what I ended up doing. It took care of my error and a few other things too. :)

//setup
const db = require('../db');
const express = require('express');
const debug = require('debug')('app:api:vote');
const Joi = require('joi');
const auth = require('../middleware/auth');
const admin = require('../middleware/admin');

const { required } = require('joi');
const router = express.Router();
router.use(express.urlencoded({ extended: false }));
router.use(express.json());

// general error handler
const sendError = (err, res) => {
  debug(err);
  if (err.isJoi) {
    res.json({ error: err.details.map((x) => x.message + '.').join('\n') });
  } else {
    res.json({ error: err.message });
  }
};
router.put('/upvote/:emojiId/', auth, async (req, res, next) => {
  let vote = {};
  try {
    const schema = Joi.object({
      emoji_id: Joi.number().required(),
      user_id: Joi.number().required(),
      vote_score: Joi.number(),
    });
    vote = await schema.validateAsync({
      emoji_id: req.params.emojiId,
      user_id: req.user.user_id,
      vote_score: 1,
    });
    if (!(await db.findUserByID(req.user.user_id))) {
      throw new Error('log in again.');
    }
    const tester = await db.findVoteByUser(vote.user_id, vote.emoji_id);
    if (!(await db.findVoteByUser(vote.user_id, vote.emoji_id))) {
      await db.upvotePost(vote);
      const upvoteScore = await db.getJustUpvotesForEmoji(vote.emoji_id);
      const message = 'message';
      upvoteScore[message] = 'Upvote sent.';
      const action = 'action';
      upvoteScore[action] = 1;
      res.json(upvoteScore);
    } else if (tester.vote_score == -1) {
      await db.upvotePut(vote);
      const upvoteScore = await db.getJustUpvotesForEmoji(vote.emoji_id);
      const message = 'message';
      upvoteScore[message] = 'Downvote changed to upvote.';
      const action = 'action';
      upvoteScore[action] = 2;
      res.json(upvoteScore);
    } else {
      await db.deleteVoteByUserIdAndEmojiId(vote);
      const upvoteScore = await db.getJustUpvotesForEmoji(vote.emoji_id);
      const message = 'message';
      upvoteScore[message] = 'Upvote deleted.';
      const action = 'action';
      upvoteScore[action] = 3;
      res.json(upvoteScore);
    }
  } catch (err) {
    sendError(err, res);
  }
});

module.exports = router;

and front end..

  $(document).on('click', '.upvote-emoji-button', (evt) => {
    const button = $(evt.currentTarget);
    const emoji_id = button.data('id');
    $.ajax({
      method: 'PUT',
      url: `/api/vote/upvote/${emoji_id}`,
      data: emoji_id,
      dataType: 'json',
    })
      .done((res) => {
        if (res.error) {
          bootbox.alert(res.error);
        } else {
          if (res.action == 1) {
            button.addClass('btn-danger').removeClass('btn-primary');
            button.parent().next().next().html(res.upvotes);
            button.parent().next().next().next().next().html(res.vote_count);
            button.parent().next().next().next().next().next().html(res.total_score);
            bootbox.alert(res.message);
          } else if (res.action == 2) {
            button.addClass('btn-danger').removeClass('btn-primary');
            button.parent().next().children().addClass('btn-primary').removeClass('btn-danger');
            button.parent().next().next().html(res.upvotes);
            button.parent().next().next().next().next().html(res.vote_count);
            button.parent().next().next().next().next().next().html(res.total_score);
            bootbox.alert(res.message);
          } else if (res.action == 3) {
            button.removeClass('btn-danger').addClass('btn-primary');
            button.parent().next().next().html(res.upvotes);
            button.parent().next().next().next().next().html(res.vote_count);
            button.parent().next().next().next().next().next().html(res.total_score);
            bootbox.alert(res.message);
          }
        }
      })
      .fail((xhr, textStatus, err) => {
        bootbox.alert(err);
        // alert(`${textStatus}\n${err}\n${xhr.status}`);
      });
  });