Randomly started receiving `Cannot read property 'read' of undefined`

[astrotars]

I randomly started seeing Cannot read property 'read' of undefined when attempting to run my script.

req.on('response', res => {
    if (res.statusCode != 200) {
        return this.emit(
            'error',
            new Error('Bad status code'),
        );
    }

    let encoding =
            res.headers['content-encoding'] || 'identity',
        charset = getParams(
            res.headers['content-type'] || '',
        ).charset;

    res = decompress(res, encoding);
    res = translate(res, charset);

    res.pipe(feedparser);
});

feedparser.on('error', done);
feedparser.on('end', done);

feedparser.on('readable', () => {
    let post;

    let siteTitle;
    let siteLink;
    let siteDescription;

    let articleLink;
    let articleTitle;
    let articleSummary;
    let articleDescription;
    let articleDate;

    while ((post = this.read())) {
        siteTitle = post.meta.title;
        siteLink = post.meta.link;
        siteDescription = post.meta.description || '';

        articleLink = post.link;
        articleTitle = strip(
            entities.decodeHTML(post.title),
        );
        articleDescription = strip(
            entities.decodeHTML(post.description),
        );
        articleDate = post.pubdate || moment().toDate();
    }
});

[danmactough]

Did you recently switch to arrow functions for the event handlers? this in arrow functions gets defined differently. For event handlers, arrow functions generally won't work if the function relies on this. https://stackoverflow.com/a/34361380

[astrotars]

Bingo! Thanks for the heads up. I didn't even think of that.

[danmactough]

🎉 consider changing references to this to refer to the appropriate variable instead: req or feedparser