numberFormat.js

function numberFormat(amount, prefix, suffixArray, maxWholeDigitLength, decimalLength) {
  var suffixIndex = 0;
  while(amount > Math.pow(10, maxWholeDigitLength) && suffixIndex < suffixArray.length) {
    amount /= 1000;
    suffixIndex++;
  }
  return prefix + amount.toFixed(decimalLength) + suffixArray[suffixIndex];
};

var dollarSuffix = ["", "K", "M", "B"];
var dollarPrefix = "$";

numberFormat(1000000, dollarPrefix, dollarSuffix, 2, 1)