const numberFormatDigits = 1;

function formatNumber(num: number): string {
  type UnitLookup = { value: number; symbol: string };
  const lookup: UnitLookup[] = [
    { value: 1, symbol: '' },
    { value: 1e3, symbol: 'K' },
    { value: 1e6, symbol: 'M' },
    { value: 1e9, symbol: 'G' },
    { value: 1e12, symbol: 'T' },
    { value: 1e15, symbol: 'P' },
    { value: 1e18, symbol: 'E' },
  ];
  const rx = /\.0+$|(\.[0-9]*[1-9])0+$/;
  let item: UnitLookup | undefined;
  for (item of lookup.slice().reverse()) {
    if (num >= item.value) break;
  }
  return item !== undefined
    ? (num / item.value).toFixed(numberFormatDigits).replace(rx, '$1') +
        item.symbol
    : num.toFixed(numberFormatDigits).replace(rx, '$1');
}