Towards a NumPy inspired bound random integer producer

randint.js

const assert = require('assert');

// Produce random (signed) integers from min inclusive to max exclusive
function randint(min = 0, max) {
  let lo = min;
  let hi = max;

  if (typeof max === 'undefined') {
    hi = lo;
    lo = 0;
  }

  if (hi < lo) {
    throw Error('min need be less than max please');
  }

  return Math.floor(Math.random() * (hi - lo)) + lo;
}

for (let i = 0; i < 100; i += 1) {
  // Calling sans arguments gives back zero no matter what
  assert.equal(randint(), 0);
}

for (let i = 0; i < 100; i += 1) {
  // Same when calling with a min of one sans max
  assert.equal(randint(1), 0);
}

// Expect min to be zero, max to be one, result to be zero
assert(randint(1) >= 0 === randint(1) < 1);

// Same when calling with a min of one sans max
assert.equal(randint(1), 0);

for (let i = 0; i < 100; i += 1) {
  // Same with null
  assert.equal(randint(null), 0);
}

for (let i = 100; i > 0; i -= 1) {
  // Try out a few ranges in the positive
  assert(randint(i) < i);
}

for (let i = -99; i < 0; i += 1) {
  // What happens when using negative parameters?
  assert(randint(2 * i, i) <= i);
}

try {
  randint(0, -10)
} catch ({ message }) {
  assert.equal(message, 'min need be less than max please');
}

# Tested with Node.js 12.18.1
git clone https://gist.github.com/1cbd1736c7f5320c11cce08c9db7ec04.git randint
cd randint
node randint.js