Format a percentage according to some arbitrary rules that actually make it pleasing to look at.

format-percentage.js

// Format a percentage according to some arbitrary rules that actually make it pleasing to look at.
// 100 -> 100            // whole numbers have no decimal
// 85.1543 -> 85.1       // it just truncates after first non-zero decimal
// 3.00345 -> 3.003      // leading zeros preserved before truncate
// 3.0000345 -> 3.00003  // ...up to a limit of 5dp
// 3.000001 -> 3         // ...so fractional numbers with 5+ leading zeros become an integer
function formatPercentage (num) {
  const [int, frac] = num.toFixed(5).split('.')
  const index = frac.split('').findIndex(n => n !== '0')
  return index === -1 ? int : `${int}.${frac.slice(0, index + 1)}`
}