index.ts

import { getCount_IndexOf } from "./indexof.ts";
import { getCount_Set } from "./set.ts";

const input =
  "hello world i am very big string maybe with vowel maybe not with wovel....";

// Performance test each function 1000000 times
const start_IndexOf = Date.now();
for (let i = 0; i < 1000000; i++) {
  getCount_IndexOf(input);
}
const end_IndexOf = Date.now();
console.log(`indexOf: ${end_IndexOf - start_IndexOf}ms`);

const start_Set = Date.now();
for (let i = 0; i < 1000000; i++) {
  getCount_Set(input);
}
const end_Set = Date.now();
console.log(`set: ${end_Set - start_Set}ms`);

indexof.ts

const vowels = ["a", "e", "i", "o", "u"];
export function getCount_IndexOf(arg: string): number {
  const list = arg.split("");
  let result = 0;

  for (let index = 0, { length } = list; index < length; ++index) {
    if (vowels.indexOf(list[index]) != -1) ++result;
  }

  return result;
}

set.ts

const vowels = new Set(["a", "e", "i", "o", "u"]);

export function getCount_Set(arg: string): number {
  const list = arg.split("");
  let result = 0;

  for (let i = 0; i < list.length; i++) {
    if (vowels.has(list[i])) ++result;
  }

  return result;
}