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JavaScript Express Basics Parameters, Query Strings, and Modularizing Routes Randomize Cards

Damian McCarthy
Damian McCarthy
3,656 Points

The ID variable comes up as undefined when I click the link, The other variable works fine though


extends layout.pug

block content

      h2= text

      if hint
          i Hint: #{hint}

      a(href='/' + `${id}?side=${sideToShow}`)= sideToShowDisplay
const express = require('express');
const router = express.Router();
const { data } = require('../data/flashcardData.json');
const cards = data.cards;

router.get('/:id', (req, res) => {
    const { side } = req.query;
    const { id } = req.params;
    const text = cards[id][side];
    const { hint } = cards[id];

    const templateData = { text };
    if (side === 'question') {
        templateData.hint = hint;
        templateData.sideToShow= 'answer';
        templateData.sideToShowDisplay= 'Answer';
    } else if (side === 'answer') {
        templateData.sideToShow= 'question';
        templateData.sideToShowDisplay= 'Question';

    res.render('cards', templateData);

module.exports = router;
Steven Parker
Steven Parker
229,921 Points

Note: Links to "localhost" only work on your own computer and cannot be shared with other students.

Damian McCarthy
Damian McCarthy
3,656 Points

I am Aware it Doesn't really matter that it says local host I was just showing the issue I was having which when the id variable is called it comes out undefined in the URL. The other portion of the URL's Variable works and when I console log it, it works.

1 Answer

You need to pass id into your render() call. Put it inside the templateData object,

const templateData = { text, id };

and you should be able to reference it from the .pug template i.e.


And remove the '/' before the ${id}, that was screwing mine up.

I got it to work without the id entirely. My code looks like this:

Damian McCarthy
Damian McCarthy
3,656 Points

Yeah, I already figured this one out.