Sorting a list of values using comparator function in Javascript

 A = [3, 8, 7, 5] B = [3, 1, 7, 19]

A.sort((a,b)=>a-b) //sorting a single array

console.log(A)

let list=[]

for(let i=0;i<A.length;i++){

    list.push([A[i],B[i]])

}

console.log(list) //creating a list from two arrays

// let A=[[2,9],[3,3],[1,5],[3,6],[3,9]] --generating a list from two arrays

// console.log(A)

//code to sort the list of elements using comparator function

//It will compare the first element in the array,

//if two elements are equal then it will compare the next element in the array.

list.sort((a,b)=>{

    // console.log(a[1])

    if(a[0]>b[0]){

        return 1

    }else

    if(a[0]<b[0]){

        return -1

    }else

    if(a[0]==b[0]){

        if(a[1]>b[1]){

            return -1

        }

        else{

            return 1

        }

    }

})

//here we are sorting the first element in ascending order,

// if both numbers are same then we are sorting the second element in decending order.

refer: mdn docs sort function for more details