Node timer with nano-second precision

test.js

const Timer = require('./timer')

const timer = new Timer();

// do stuff...

timer.stop();

// '1s, 589.334334 ms'

timer.js

class Timer {
  constructor() {
    this.start();
    this.stoppedAt = null;
    this.totalNanoSeconds = 0;
  }

  start() {
    this.absStartedAt = process.hrtime();
    this.startedAt = process.hrtime();
  }

  stop() {
    this.stoppedAt = process.hrtime(this.startedAt);
    return this.format(this.stoppedAt);
  }

  lap() {
    this.stoppedAt = process.hrtime(this.startedAt);
    this.startedAt = process.hrtime();
    return this.format(this.stoppedAt);
  }

  total() {
    return this.format(process.hrtime(this.absStartedAt));
  }

  format(t, decimals = 8) {
    t = t || this.stoppedAt;
    const ret = [];
    if (this.stoppedAt[0] > 0) {
      ret.push(`${this.stoppedAt[0]}s`);
    }
    const ms = this.stoppedAt[1] / 1e6;
    if (ms > 1) {
      ret.push(`${parseFloat(ms.toFixed(decimals))} ms`);
    } else if (ms > 0.1) {
      ret.push(`${parseFloat((ms * 100).toFixed(decimals))} μs`);
    } else if (ms > 0.01) {
      ret.push(`${parseFloat((ms * 1e6).toFixed(decimals))} ns`);
    }
    return ret.join(', ');
  }
}

module.exports = Timer;