Google spreadsheet function to calculate the value of a CryptoCurrency using coinmarketcap API

coinMarketCap.googleSpreadsheet.js

/**
* Return a cryptocurrency value in USD using coinmarketcap API
*
* @param string currency e.g. BTC, ETH
* 
* @return float  value
*/
function coinmarketcap(currency)
{
   var body = UrlFetchApp.fetch("https://api.coinmarketcap.com/v1/ticker/");
   var json = JSON.parse(body);

   currencyToValue = {};
   for (var i=0, l = json.length; i<l; i++) { 
     var row = json[i];
     if (currency === row.symbol) {
       return  row.price_usd;
     }
   }
}