next.js/packages/next/src/build/duration-to-string.ts

export function durationToString(compilerDuration: number) {
  let durationString
  if (compilerDuration > 120) {
    durationString = `${(compilerDuration / 60).toFixed(1)}min`
  } else if (compilerDuration > 40) {
    durationString = `${compilerDuration.toFixed(0)}s`
  } else if (compilerDuration > 2) {
    durationString = `${compilerDuration.toFixed(1)}s`
  } else {
    durationString = `${(compilerDuration * 1000).toFixed(0)}ms`
  }
  return durationString
}