Here is a simple way to convert large numbers into an easily readable string. This is useful for displaying large numbers to the user. For example: 200000 --> "200k" 1200000 --> "1.2M" 54100000000 --> "54.1B"

readifyNumbers

var readifyNumbers = function(number) {
  /* READIFYNUMBERS ASSUMPTIONS:
    - Numbers will have typeof number or string
    - No commas (expects format to be: 1500000)
  */

  // throw error for any parameter input that is not a number and cannot be converted into a number
  if (Number(number).toString() === 'NaN') {
    throw 'Error. The readifyNumbers input parameter must be a number.';
  }

  // convert input number to string and remove anything after the decimal
  var numberString = Math.floor(number).toString();

  // find digits length
  var digitsLength = numberString.length;

  // check length (to determine whether to convert to thousands or millions)
  if (digitsLength <= 3 && digitsLength !== 0) {
    return trimToTenths( number.toString() );
  } else if (digitsLength <= 6) {
    number = number/1000;
    return trimToTenths( number.toString() ) + 'k';
  } else if (digitsLength <= 9) {
    number = number/1000000;
    return trimToTenths( number.toString() ) + 'M';
  } else if (digitsLength <= 12) {
    number = number/1000000000;
    return trimToTenths( number.toString() ) + 'B';
  } else {
    console.log('Only numbers with a string length between 1-12 digits before the decimal will be converted to a readable number.');
    return number.toString();
  }

  // helper functions
  function trimToTenths(stringifiedNumber) {
    var index = stringifiedNumber.indexOf('.');
    if (index === -1) {
      return stringifiedNumber;
    } else {
      var slicedNum = stringifiedNumber.slice(0, index + 3); // slices an extra digit so that it can be rounded
      var roundedNum = Math.round(Number(slicedNum) * 10) / 10; // multiply, then divide by 10 as a quick hack to round to the tenths place
      return roundedNum.toString();
    }
  }
};