JS: format number with metric prefix 📜

Format Number with Metric Prefix

/*
format number with metric prefix, e.g. 1.2 k
n is integer. The number to be converted
m is integer. The number of decimal places to show. Default to 1.
returns a string, with possibly one of k M G T ... suffix.

http://xahlee.info/js/js_format_number.html
Version: 2019-04-15
 */

const xah_format_number = (n, m = 1) => {
 const prefix = [
  "",
  " k",
  " M",
  " G",
  " T",
  " P",
  " E",
  " Z",
  " Y",
  " * 10^27",
  " * 10^30",
  " * 10^33",
 ]; // should be enough. Number.MAX_VALUE is about 10^308
 let ii = 0;
 while ((n = n / 1000) >= 1) ii++;
 return (n * 1000).toFixed(m) + prefix[ii];
};

// s------------------------------
// test

console.assert(xah_format_number(111, 1) === "111.0");
console.assert(xah_format_number(111222, 1) === "111.2 k");
console.assert(xah_format_number(111222333, 1) === "111.2 M");
console.assert(xah_format_number(111222333444, 1) === "111.2 G");
console.assert(xah_format_number(111222333444) === "111.2 G");
console.assert(xah_format_number(111222333444, 3) === "111.222 G");
console.assert(xah_format_number(111222333444, 0) === "111 G");