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scrape_cmc.js
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scrape_cmc.js
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let fs = require('fs');
let axios = require('axios');
let cheerio = require('cheerio');
let cheers = require('cheers');
let json2csv = require('json2csv');
const getHistoryLinks = (url) => {
return axios(url).then((response) => {
let html = response.data;
let $ = cheerio.load(html, {ignoreWhitespace: true});
let link = "";
let links = [];
let historyLink = false;
let historyLinks = [];
$('a').each(function(i, elem) {
link = $(this).attr('href');
historyLink = (link && link.length === 21) ? true : false
if (historyLink) { historyLinks.push('https://coinmarketcap.com'+link) }
});
return historyLinks;
}).catch((error) => console.log(error));
};
const getData = (historyLinks) => {
// historyLinks = historyLinks.slice(0,2); // trim load for testing
console.log('historyLinks:\n', historyLinks);
let config = {
url: historyLinks,
blockSelector: "tr",
scrape: {
currency: {
selector: "td.no-wrap.currency-name > a",
extract: "text"
},
symbol: {
selector: "td.text-left",
extract: "text"
},
marketcap: {
selector: "td.no-wrap.market-cap.text-right",
extract: "text"
},
price_usd: {
selector: 'td:nth-child(5) > a',
extract: "text"
},
supply: {
selector: 'td:nth-child(6) > a',
extract: "text"
},
volume: {
selector: 'td:nth-child(7) > a',
extract: "text"
},
change_1hr: {
selector: 'td.no-wrap.percent-1h.positive_change.text-right',
extract: "text"
},
change_1day: {
selector: 'td:nth-child(9)',
extract: "text"
},
change_1week: {
selector: 'td:nth-child(10)',
extract: "text"
}
}
};
return cheers.scrape(config).then((results) => {
cmcData = results.reduce((data, arr, i) => {
date = `${historyLinks[i].slice(-9, -1)}`;
data[date] = arr.splice(1, arr.length);
return data
}, {});
Object.keys(cmcData).map((i) => {
cmcData[i].map((o) => {
Object.keys(o).map((i) => {
o[i] = o[i].trim();
});
});
});
return cmcData
}).catch((error) => console.error(error));
};
const formatData = (cmcData) => {
data = [];
Object.keys(cmcData).forEach(date => {
cmcData[date].forEach(stats => {
stats.date = date;
data.push(stats);
})
})
let fields = ['date'].concat(Object.keys(cmcData[Object.keys(cmcData)[0]][0])).slice(0,-1);
let csv = json2csv({ data, fields });
return csv;
}
const outputData = (csv) => {
console.log('csv:\n', csv);
fs.writeFile('scrape_cmc.csv', csv, (err) => {
if (err) throw err;
console.log('file saved');
});
};
const scrapeSite = async (url) => {
try {
const historyLinks = await getHistoryLinks(url);
const cmcData = await getData(historyLinks);
const csv = formatData(cmcData);
outputData(csv);
} catch (error) {
console.log(error);
}
};
scrapeSite('https://coinmarketcap.com/historical/');