I'm learning how to measure performance, and would like to use some code that takes about 1-2 seconds to pute.

I've used this code below taken from Mozilla, but I wonder if someone could help me out with an operation that's a little more concise. It doesn't have to "make sense".

const iterations = 50;
const multiplier = 1000000000;

function calculatePrimes(iterations, multiplier) {
  var primes = [];
  for (var i = 0; i < iterations; i++) {
    var candidate = i * (multiplier * Math.random());
    var isPrime = true;
    for (var c = 2; c <= Math.sqrt(candidate); ++c) {
      if (candidate % c === 0) {
        // not prime
        isPrime = false;
        break;
      }
    }
    if (isPrime) {
      primes.push(candidate);
    }
  }
  return primes;
}

function doPointlessComputationsWithBlocking() {
  var primes = calculatePrimes(iterations, multiplier);
  pointlessComputationsButton.disabled = false;
  console.log(primes);
}

I'm learning how to measure performance, and would like to use some code that takes about 1-2 seconds to pute.

I've used this code below taken from Mozilla, but I wonder if someone could help me out with an operation that's a little more concise. It doesn't have to "make sense".

const iterations = 50;
const multiplier = 1000000000;

function calculatePrimes(iterations, multiplier) {
  var primes = [];
  for (var i = 0; i < iterations; i++) {
    var candidate = i * (multiplier * Math.random());
    var isPrime = true;
    for (var c = 2; c <= Math.sqrt(candidate); ++c) {
      if (candidate % c === 0) {
        // not prime
        isPrime = false;
        break;
      }
    }
    if (isPrime) {
      primes.push(candidate);
    }
  }
  return primes;
}

function doPointlessComputationsWithBlocking() {
  var primes = calculatePrimes(iterations, multiplier);
  pointlessComputationsButton.disabled = false;
  console.log(primes);
}

• javascript
• performance

• 1 sort a very large array. you don't have to write your own sort because JS has a sort function. – user6713871 Commented Jun 27, 2020 at 7:39

1 Answer 1

The easiest way to make an operation where the purpose is "it takes time", is to just do nothing but for a time period:

function wait(seconds) {
  var start = new Date();
  //empty while loop until the required amount of time has passed
  while((new Date() - start) / 1000 < seconds);
}

var begin = performance.now();

console.log("start");

wait(2);

console.log("finish in", performance.now() - begin, "ms");

If you need it to be not as certain, you can add or modify the time to wait by a random amount:

function wait(seconds) {
  // add or subtract up to 50% 
  seconds *= Math.random() + 0.5;
  var start = new Date();
  while((new Date() - start) / 1000 < seconds);
}

var begin = performance.now();

console.log("start");

wait(2);

console.log("finish in", performance.now() - begin, "ms");