Top 20 Cryptocurrency Market Cap Weighted Algorithm

marketCapWeighted.js

const request = require('request');
const Table = require('cli-table');
// Algorithm will run every 5 seconds
setInterval( () =>{
// API request to Coin Market Cap for top 20 cryptocurrencies
request('https://api.coinmarketcap.com/v1/ticker/', function(error, response, body) {
    
    const chart = JSON.parse(body);   
    // The cap of how much of the portfolio could allocate to a certain cryptocurrency (0.05 = 5%)
    // no cryptocurrency will surpass this cap amount in portfolio allocation.
    const cap = 0.10; 
    const top20 = [];
    // Place the top 20 cryptocurrencies to an array.
    for (let i = 0; i < 20; i++) {
        top20.push(chart[i]);
    }
    // Sum the top 20 cryptocurrencies market cap
    let total20Cap = 0;
    top20.forEach( crypto => {
        total20Cap += Number(crypto.market_cap_usd);
    });

    const _table = new Table({
        chars: { 'top': '═' , 'top-mid': '╤' , 'top-left': '╔' , 'top-right': '╗'
               , 'bottom': '═' , 'bottom-mid': '╧' , 'bottom-left': '╚' , 'bottom-right': '╝'
               , 'left': '║' , 'left-mid': '╟' , 'mid': '─' , 'mid-mid': '┼'
               , 'right': '║' , 'right-mid': '╢' , 'middle': '│' }
      });
      
      _table.push(
          ['Cryptocurrency', 'Market Cap', 'Market Cap Ratio']
      );

    // Create the ratios of a cryptocurrency's market cap and the top 20 cryptocurrencies
    const allocations = [];
    top20.forEach( crypto => {
        _table.push([crypto.name, crypto.market_cap_usd, (Number(crypto.market_cap_usd) / Number(total20Cap))]);

        allocations.push({
            'cryptocurrency': crypto.name,
            'market_cap': crypto.market_cap_usd,
            'ratio': (Number(crypto.market_cap_usd) / Number(total20Cap)) 
        });
    });

    
      
    // Print out our results in the console
    console.log("======= Top 20 Cryptocurrency Market Caps =================");
    console.log(_table.toString());

    // Perform Cap Weighted Algorithm
    for(let i = 0; i < allocations.length; i++) {
        let alloc = allocations[i];
        
        // If the ratio of cryptocurrency market cap to top 20 cryptocurrency is greater than the cap
        if (alloc.ratio > cap){
            let overflow = Number(alloc.ratio - cap);

            // Set the allocation of this cryptocurrency to the cap
            alloc.ratio = cap;

            // Create a new array to spread the appropriate allocation with the overflow from cryptocurrency
            // that surpassed the cap.
            let remainder = allocations.slice(i+1);

            // Sum up the cryptocurrencies market cap that need their allocation to be calculated
            let total_nested_cap = 0;
            remainder.forEach( crypto => {
                total_nested_cap += Number(crypto.market_cap);
            });

            // Give the remaining cryptocurrencies the overflow of allocation from this cryptocurrency based on 
            // the ratios of the remaining cryptocurrencies.
            for(let j = 0; j < remainder.length; j++) {
                let remainder_crypto = remainder[j];
                let cap_fraction = Number(remainder_crypto.market_cap) / Number(total_nested_cap);
                allocations[i+j+1].ratio += overflow * cap_fraction;
            };
        }
    }
    const table = new Table({
        chars: { 'top': '═' , 'top-mid': '╤' , 'top-left': '╔' , 'top-right': '╗'
               , 'bottom': '═' , 'bottom-mid': '╧' , 'bottom-left': '╚' , 'bottom-right': '╝'
               , 'left': '║' , 'left-mid': '╟' , 'mid': '─' , 'mid-mid': '┼'
               , 'right': '║' , 'right-mid': '╢' , 'middle': '│' }
      });
      
      table.push(
          ['Cryptocurrency', 'Market Cap', 'Portfolio Allocation']
      );
      
    // See if the allocations sum up to ~100%
    let check = 0;
    for( let k = 0; k< allocations.length; k++){
        table.push([allocations[k].cryptocurrency, allocations[k].market_cap, allocations[k].ratio])
        check += allocations[k].ratio;
    }
    console.log(table.toString());


});
}, 5000);