function commas() {
var key = 'api';
var secret = 'secret';

var baseUrl = "https://exchange.com";
var endPoint = "/public/api/ver1/smart_trades";
var pointParams = "?account_id=xxx&scope=finished";
var queryString = endPoint + pointParams;
var signature = Utilities.computeHmacSha256Signature(queryString, secret);
signature = signature.map(function(e) {return ("0" + (e < 0 ? e + 256 : e).toString(16)).slice(-2)}).join("");

var hparams = {
    'method': 'get',
    'headers': {'APIKEY': key,
                'Signature': signature},
    'muteHttpExceptions': true
};

var data = chunk(UrlFetchApp.fetch(baseUrl + queryString , hparams).getContentText(),5000);
Logger.log(data)
var ss = SpreadsheetApp.getActive();
var sheet = ss.getSheetByName("rates");
var raw = sheet.getRange(13,1).offset(0, 0, data.length).setValue(data)
}
function chunk(a,b){
  return Array.apply(null, new Array(Math.ceil(a.length/b))).
  map(function (c, d) {return [a.substr(d*b,b)];});
}

var data = BtwBraces(UrlFetchApp.fetch(baseUrl + queryString , hparams).getContentText());

function BtwBraces(a){
  return a.split(/[{}]/g).
  filter(function(a){return a;}).
  map(function (a){return [a];})
}

function myFunction() {
    var ss = SpreadsheetApp.getActive();
    var sheet = ss.getSheetByName("Лист1");
    var data = BtwBraces(Array.apply(null, Array(3000)).reduce(function(a, b) {
        return a + "{" + Array.apply(null, Array(Math.floor(Math.random() * 20) + 1)).reduce(function(a, b) {
            a.push("\"" + Array.apply(null, Array(2)).reduce(function(a, b) {
                a.push(Math.random(this).toString(36).slice(2, Math.floor(Math.random() * 10) + 3));
                return a
            }, []).join("\":\"") + "\"");
            return a
        }, []).join(",") + "}"
    }, ""));
    var raw = sheet.getRange(1, 1).offset(0, 0, data.length).setValues(data);
}
function BtwBraces(a) {
    return a.split(/[{}]/g).
    filter(function(a) {return a}).
    map(function(a) {return [a]})
}