function numberFormatter(num, digits) {
  const si = [
    { value: 1E18, symbol: 'E' },
    { value: 1E15, symbol: 'P' },
    { value: 1E12, symbol: 'T' },
    { value: 1E9, symbol: 'G' },
    { value: 1E6, symbol: 'M' },
    { value: 1E3, symbol: 'k' },
  ]
  for (let i = 0; i < si.length; i++) {
    if (num >= si[i].value) {
      return (num / si[i].value + 0.1).toFixed(digits).replace(/\.0+$|(\.[0-9]*[1-9])0+$/, '$1') + si[i].symbol
    }
  }
  return num.toString()
}
Number formatting
like 10000 => 10k
@param {number} num
@param {number} digits