Simulate stress on javascript execution by spin locking intermittently

stress.js

'use strict';

module.exports = function stress(interDelay, spinDelay, duration) {
  var spinLock = function(spinDuration) {
    var start = Date.now();
    while (Date.now() - start < spinDuration) {
      // Do nothing
    }
  };

  var approximate = function(x) {
    return (1.0 + 0.75 * (2 * Math.random() - 1)) * x;
  };

  var active = true;

  setTimeout(function() {
    active = false;
  }, duration);

  var loop = function() {
    if (!active) {
      return;
    }

    setTimeout(function() {
      spinLock(approximate(spinDelay));
      loop();
    }, approximate(interDelay));
  }

  loop();
};