Counting Sort implementation in JavaScript

counting-sort-alternative.js

function countingSort(inputArray) {
  const max = Math.max(...inputArray);
  const counters = new Array(max+1).fill(0); // or Int32Array without fill
  // count
  inputArray.forEach(inputValue => {
  	counters[inputValue]++;
  });
  // accumulate
  for(let i = 1; i<counters.length; i++) {
    counters[i] = counters[i] + counters[i-1];
  }
  // shift
  for(let i = counters.length-1; i>=0; i--) {
  	i === 0? counters[i] = 0 : counters[i] = counters[i-1];
  }
  const result = new Array(inputArray.length);
  for(let i = 0; i<inputArray.length; i++) {
    const inputValue = inputArray[i];
    const startingIndex = counters[inputValue];
    result[startingIndex] = inputValue;
    counters[inputValue]++;
  }
  return result;
}

/*
function testCase() {
	const input = [4,2,2,8,3,3,1];
	const expected = [1,2,2,3,3,4,8];
	const actual = countingSort(input);
	if(actual.toString() !== expected.toString()) {
		throw new Error(`Expected ${expected.toString()} got ${actual.toString()}`)
	}
}

testCase();
*/

counting-sort.js

function countingSort(arr) {
	const max = Math.max(...arr);
	const counters = new Array(max+1);
	counters.fill(0);
	arr.forEach(inputItem => {
		counters[inputItem]++;
	});
	for(let i = 1; i<counters.length; i++) {
		counters[i] += counters[i-1];
	}
	const output = new Array(counters.length);
	arr.forEach(inputItem => {
		const count = counters[inputItem];
		output[count-1] = inputItem;
		counters[inputItem]--;
	})
	const result = new Array(arr.length);
	arr.forEach((inputItem, i) => {
		result[i] = typeof output[i] !== `undefined` ? output[i] : inputItem;
	});
	return result;
}

/*
function testCase() {
	const input = [4,2,2,8,3,3,1];
	const expected = [1,2,2,3,3,4,8];
	const actual = countingSort(input);
	if(actual.toString() !== expected.toString()) {
		throw new Error(`Expected ${expected.toString()} got ${actual.toString()}`)
	}
}

testCase();
*/