const reverse = str => str.split('').reverse().join('');
reverse('hello world');     
// Result: 'dlrow olleh'

const getTimezone = () => Intl.DateTimeFormat().resolvedOptions().timeZone;

// Example
getTimezone();

new StringBuilder(hi).reverse().toString()

import React, { useState } from 'react' import Welcome from '../components/Welcome'  function About() {  	const [showWelcome, setShowWelcome] = useState(false)  	return ( 	<div> 	{showWelcome ? <Welcome /> : null} 	</div> 	<div> 	{showWelcome && <Welcome /> } 	</div> 	) }  export default App

let nums = [1,2,3,1]

var containsDuplicate = function(nums) {
    let obj = {};
    for(let i =0; i< nums.length; i++){
        if(obj[nums[i]]){
            obj[nums[i]] += 1;
            return true;
        }else{
            obj[nums[i]] = 1;
        }
    }
    return false;
};

console.log(containsDuplicate(nums));

// Or
const randomColor = () => `#${(~~(Math.random()*(1<<24))).toString(16)}`;
console.log(randomColor);