Given both that the question which created the numeraljs directly links to the Numeral.js site, and that 5 of the 9 questions tagged numeraljs were also tagged numeral.js, I went ahead and merged the two tags with the .js version as the parent tag.

I also created a synonym directing from numeraljs to numeral.js which will prevent someone from creating a dot-less version in future (since it already exists).

If someone is knowledgeable and so inclined to create a better tag wiki excerpt which provides actual usage guidance and a tag wiki which doesn't plagiarise the documentation that'd probably be of value as well.

Numeral.js has this built in. It can be easily achieved using a such as .format('0.00a').

Some full examples:

numeral(1000000).format('0a') will return 1m

numeral(250500).format('0.0a') will return 250.5k

numeral(10500).format('0.00a') will return 10.50k

At lines 67 and 68 of the un–minified code there is:

// figure out what kind of format we are dealing with
if (format.indexOf('$') > -1) { // currency!!!!!

So yes, it seems "$" is the only currency symbol recognised. You can add the currency symbol separately, e.g.:

var amount = '£' + numeral(2456.01231).format('0,0[.]00');

console.log(amount); // £2,456.01

or extend the library to deal with other currency symbols.

It may be better to use the ISO symbol GBP, which is not ambiguous. There are many currencies that use the £ symbol, as there are many that use $.

In this case you will need to use a different format string depending on the size of the original number. It looks like you have the following cases:

• If the number is under 1000, return the same number in long format but with at most two decimal places.
• If the number is between 1000-10,000, return the same number in long format with no decimal places.
• If the number is between 10,000-1,000,000, return the same number in shorthand format, with at most one decimal place.
• If the number is larger than 1,000,000, return the same number in shorthand format, with at most two decimal places.

For each of these cases you will need a different format string. You can do that by comparing the number to each threshold and setting the format string depending on its size.

function formatValue(value, shorthandFormat = true, shorthandLength = 5) {
  if (value === undefined || value === null) return '?';

  let valueString = value.toString();
  if (valueString.trim() === '') return '';

  let numeralValue = numeral(value)

  // Note the format changes depending on how large the value is.
  let formatter = "0[.][00]" // Default formatter: returns the same number with at most, two decimals.
  if (value > 1000) formatter = "0" // Over 1000: remove any decimal part.
  if (value > 10000) formatter = "0.[0]a" // Over 10000: use shorthand with at most, one decimal.
  if (value > 1000000) formatter = "0.[00]a" // Over 1000000: use shorthand with at most, two decimals.

  let formattedValue = numeralValue.format(formatter);

  return formattedValue;
}

const tests = [
  // Small numbers contain at most, two decimals.
  [0, "0"],
  [1, "1"],
  [1.1, "1.1"],
  [1.11, "1.11"],
  [1.115, "1.12"],
  [11.1, "11.1"],
  [11.11, "11.11"],
  [16.75, "16.75"],
  [675, "675"],
  [675.5, "675.5"],
  [675.55, "675.55"],
  
  // Numbers between one-thousand and ten-thousand may not contain decimals.
  [6700.05, "6700"],
  [2522.25, "2522"],
  [6000, "6000"],
 
  // Numbers between ten-thousand and one-million should use shorthand, with at most one decimal.
  [67500.89, "67.5k"],
  [67530.85, "67.5k"],
  [210500, "210.5k"],
  [210000, "210k"],
  
  // Numbers greater than one-million should use shortand, with at most two decimals.
  [2120000, "2.12m"],
  [6750000, "6.75m"],  
  [2000000, "2m"],
  [2100000, "2.1m"],
  [2010000, "2.01m"],
  [2001000, "2m"],
]

tests.forEach(([input, output]) => console.log(`${formatValue(input) === output ? "PASS" : "FAIL"}: ${input} --> ${formatValue(input)}. Expected: ${output}`));

<script src="https://cdnjs.cloudflare.com/ajax/libs/numeral.js/2.0.6/numeral.min.js"></script>

Note: The test for number 67500.89 was changed to expect 67.5k as the result, since 6.7k seemed to be a typo.