Why is this UrlFetch function not working properly?

问题

This is the function I'm trying to run through the JavaScript Tool on my Google Spreadsheet chart, the function is currently working on 4 different websites, where in this example:

$id is the imported value from my spreadsheet cell (belacoin)

function CoinmarketcapPrice($id) {
  var response = UrlFetchApp.fetch("https://api.coinmarketcap.com/v1/ticker/" + $id);
  var html = JSON.parse(response.getContentText());
  try 
  {
    return parseFloat(html["price_btc"]);
  }
  catch(err)
  {
    return null;
  }
}

this is what that UrlFetch returns:

[
    {
        "id": "belacoin", 
        "name": "BelaCoin", 
        "symbol": "BELA", 
        "rank": "176", 
        "price_usd": "0.212823", 
        "price_btc": "0.00008400", 
        "24h_volume_usd": "534995.0", 
        "market_cap_usd": "7694903.0", 
        "available_supply": "36156350.0", 
        "total_supply": "36156350.0", 
        "percent_change_1h": "0.63", 
        "percent_change_24h": "1.88", 
        "percent_change_7d": "-17.03", 
        "last_updated": "1499549044"
    }
]

回答1:

try html.price_btc or html[0].price_btc

回答2:

It looks like that endpoint is returning an array of objects, so if you want to access the first item in the array change your try block to:

try {
  return parseFloat(html[0]["price_btc"]);
}

回答3:

return html[0].price_btc;

made it work, thank you all!

来源：https://stackoverflow.com/questions/44997630/why-is-this-urlfetch-function-not-working-properly