// preset
const COUNT       = 1e6;
const BOUND_UPPER = 1000;
const BOUND_LOWER = 0;

const emitRandom = () => (BOUND_LOWER + Math.random() * (BOUND_UPPER - BOUND_LOWER + 1)) | 0;

const vector = [];

let vector1;
let vector2;
let start;

console.log('Program starts.');

// fill array with pseudo-random numbers, it's enough for current purpose
for ( let index = 0; index < COUNT; index += 1 ) vector.push(emitRandom());

// create two clones from original array
vector1 = [...vector];
vector2 = [...vector];

console.log(`Array of ${COUNT} random integers is generated.`);

/**** native Array.prototype.sort ****/

console.log('Test native JavaScript realization of Array.prototype.sort.');

start = Date.now();

vector1.sort((a, b) => a - b);

console.log('Time to sort with Array.prototype.sort: ', Date.now() - start);

/**** Counting sort ****/

start = Date.now();

const tmpVector = Array(BOUND_UPPER + 1).fill(0);

for ( let index = 0; index < COUNT; index += 1 ) tmpVector[vector2[index]] += 1;

// There is one interesting thing, look at temporary vector created above attentively.
// Each element in it represents the number of generated values in original vector equal to the value of corresponding index.
// It's about probability distribution in Math.random() implementation.

let _index = 0;

for ( let index = 0; index <= BOUND_UPPER; index += 1 ) {
    for ( let subIndex = 0; subIndex < tmpVector[index]; subIndex += 1 ) {
        vector2[_index] = index;
        _index += 1;
    }
}

console.log('Time to sort with Counting sort: ', Date.now() - start);

// ensure vector1 and vector2 are identical
console.assert(JSON.stringify(vector1) === JSON.stringify(vector2), 'Two sorted arrays has different elements order!');
console.log(`Are both sorts produce the identical result? - ${['No', 'Yes'][Number(vector1.length === vector2.length && vector1.every((item, index) => item === vector2[index]))]}`);

console.log('Program ends.');