Simple and compact NodeJS performance marking class.

perf.js

const util = require('util');

const HOT_SPOT_MIN = 100; // amount in ms to determine if there's a hot spot

function getStackLine(rewind) {
  const stackRewind = rewind || 0;
  const stack = new Error().stack;
  const line0 = stack.split('\n')[stackRewind + 1];
  const sub0 = line0.indexOf('/');
  const sub1 = line0.lastIndexOf(':');
  return line0.substring(sub0, sub1);
}

const perfObj = function constructor(id, name) {
  this.id = id || Math.floor(Math.random() * 10000);
  this.name = name || `perf_${this.id}`;
  this.start = Date.now();
  this.stack = [{ ref: getStackLine(2), ts: 0, name: 'create' }];
  this.length = 1;
};

perfObj.prototype.addRef = function addRef(name) {
  const ticks = Date.now() - this.start;
  const entry = { ref: getStackLine(2), ts: ticks };
  if (name) {
    entry.name = name;
  }
  if (ticks - this.stack[this.stack.length - 1].ts > HOT_SPOT_MIN) { 
    entry.hot = true;
  }
  this.stack.push(entry);
  this.length = this.stack.length;
};

perfObj.prototype.print = function print() {
  // TODO: Allow summary
  const output = util.inspect(this.get(), { showHidden: false, depth: null, colors: true });
  console.log(output);
};

perfObj.prototype.get = function get() {
  return { id: this.id, name: this.name, start: this.start, stack: this.stack };
};

module.exports = perfObj;