Sorting Array with JavaScript reduce function

Question

Often I study some JavaScript interview questions, suddenly I saw a question about usage of reduce function for sorting an Array, I r

Answer 1

Here is an example of the sorting an array in descending order using reduce function.

what is the initialValue of reduce function

In this below function the initial value is the [] which is passed as thisArg in the reduce function.

 array.reduce(function(acc,curr,currIndex,array){
        //rest of the code here
        },[]//this is initial value also known as thisArg)

So basically an empty array is passed and the elements will be be pushed to this array

The accumulator here is the empty array.

const arr = [91, 4, 6, 24, 8, 7, 59, 3, 13, 0, 11, 98, 54, 23, 52, 87, 4];
var m = arr.reduce(function(acc, cur) {
  // this arrVar will have the initial array
  let arrVar = arr;
  // get the max element from the array using Math.max
  // ... is spread operator
  var getMaxElem = Math.max(...arrVar);
  // in the accumulator we are pushing the max value
  acc.push(getMaxElem);
  // now need to remove the max value from the array, so that next time it 
  // shouldn't not be considered
  // splice will return a new array
  // now the arrVar is a new array and it does not contain the current
  // max value
  arrVar = arrVar.splice(arrVar.indexOf(getMaxElem), 1, '')
  return acc;
}, []);
console.log(m)