Merge Sort

function mergeSort(arr){
    if (arr.length===1){
        return arr;
    }
    
    let len= arr.length;
    let middle= Math.floor(len/2);
    let left=arr.slice(0,middle);
    let right=arr.slice(middle);
    
    return merge(mergeSort(left), mergeSort(right));

}

function merge(left, right){
    
    let leftIndex=0, rightIndex=0;
    let resultArr=[];
    while(leftIndex<left.length&& rightIndex< right.length){
        if(left[leftIndex]<right[rightIndex]){
            resultArr.push(left[leftIndex]);
            leftIndex++;
        }
        
        else{
            resultArr.push(right[rightIndex]);
            rightIndex++;
        }
    }
    
    return resultArr.concat(left.slice(leftIndex)).concat(right.slice(rightIndex));
    
}
console.log(mergeSort([2, 8, 1, 3, 6, 7, 5, 4]));