stock-on-the-news.ts

import axios from 'axios';
import * as Parser from 'rss-parser';
import * as cheerio from 'cheerio';

const rss = new Parser();

interface Article {
    title: string;
    url: string;
}

interface ParsedArticle {
    title: string,
    url: string,
    desc: string,
    date: string,
    quotes: string[]
}

type Optional<T> = T | null;

async function getArticlesUrls(sources: string[]): Promise<Article[]> {
    const promises = await sources.map(async (src: string) => {
        const feed = await rss.parseURL(src);
        return feed.items.map(item => {
            return {
                title: item.title,
                url: item.link
            };
        });
    });
    const raw = await Promise.all(promises);
    return raw.reduce((urls: Article[], articles: Article[]) => {
        return urls.concat(articles);
    }, []);
};

async function parseArticle(article: Article): Promise<Optional<ParsedArticle>> {
    const response = await axios.get(article.url);
    const html = response.data;
    const $ = cheerio.load(html);
    const quotes = $('span.quote');
    if (!quotes.length) return null;
    const desc = quotes.parent('p').text().replace(/\s\s+/g, ' ');
    const published = $('.timestamp span').text().trim();
    const stocks = quotes.map(function(idx, item){return $(this).text().trim();}).get();
    return <ParsedArticle>{
        title: article.title,
        url: article.url,
        desc: desc,
        date: published,
        quotes: stocks
    };
};

async function parseArticles(articles: Article[]): Promise<ParsedArticle[]> {
    const promises = articles.map(async (item: Article) => {
        const article: Optional<ParsedArticle> = await parseArticle(item);
        return article;
    });
    const result = await Promise.all(promises);
    return result.reduce((arr: ParsedArticle[], item: Optional<ParsedArticle>) => {
        if (item) arr.push(item);
        return arr;
    }, []);
};

(async function() {
    const sources: Array<string> = [
        "http://feeds.marketwatch.com/marketwatch/topstories/",
        "http://feeds.marketwatch.com/marketwatch/marketpulse/"
    ];
    const articles: Article[] = await getArticlesUrls(sources);
    const result = await parseArticles(articles);
    console.log(result);
})();