SOURCE

const findFirst=(str)=>{
    let map = new Map();
    for(let char of str) {
        map.set(char,map.has(char)?map.get(char)+1:1);
    }
    for(let i=0;i<str.length;i++) {
        if(map.get(str[i])===1) return i;
    }
    return -1;
}
const Input = "loveleetcodev"
// console.log(findFirst(Input))

const reverseStr=(str)=>{
    let temp = str.trim();
    let right = temp.length-1;
    let left = 0;
    let ans = "";
    while(right>=0) {
        left = right-1;
        while(left>=0&&temp[left]!==" ") left--;
        ans+= temp.slice(left+1,right+1)+" ";
        right = left-1;
    }
    return ans.trim()
}
const str = "  the sky  is  blue  "
// console.log(reverseStr(str));

const flatten=(arr)=>{
    let ans = [];
    for(let item of arr) {
        Array.isArray(item)?
        ans.push(...flatten(item))
        :ans.push(item);
    }
    return ans;
}
// console.log(flatten([1, [2, [3, 4], 5], 6]));

const frequency=(str)=>{
    const map = new Map()
    let ans = "";
    for(let char of str) {
        map.set(char,map.has(char)?map.get(char)+1:1)
    }
    let temp = Array.from(map).sort((a,b)=>b[1]-a[1]);
    for(let [key,value] of temp) {
        ans+=key.repeat(value);
    }
    return ans;
}
const str2="Aabbddddcbc"
console.log(frequency(str2));