SOURCE

let arr = [0,9,7,5];

function sort(arr){
    if(arr.length < 2) return arr;
    let midIndex = Math.floor(arr.length/2);
    let midValue = arr.splice(midIndex,1)[0];
    let left = [];
    let right = [];
    for(let i=0;i<arr.length;i++){
        if(arr[i]<midValue){
            left.push(arr[i])
        }else{
            right.push(arr[i]);
        }
    }
    return [...sort(left),midValue,...sort(right)];
}

console.log(sort(arr))