Flatten a nested array in sorted order

flattenNestedArrAndSort.js

// Input
// [5, 10, 11, [2, 8], [12, 1, 4], [9, [5,4, 12]], 17]
// Output
// [1, 2, 4, 5, 8,9,10, 11, 12, 17]

function isArray(value) {
	return value instanceof Array;
}

function getgetFlatArray2(arr) {
for (var i = 0; i < arr.length; i++) {
	if (isArray(arr[i])) {
  	
  }
}
}

function getFlatArray(arr, index = 0, newArr = []) {
	
}
function getFlatArray(arr, index = 0, newArr = []) {
	var currVal = arr[index];
  if (isArray(currVal)) {
  	return getFlatArray(currVal);
  }
	newArr.push(currVal);
  if (index === arr.length - 1) {
  	return newArr;
  }
  return getFlatArray(arr, index + 1, newArr);
}

function getSortedArray(arr, index = 0, newArr = []) {
	var currVal = arr[index];
  var prevVal = newArr[index - 1];
  if (index) {
  	newArr.push(currVal);
  } else if (currVal > prevVal) {
  	newArr.push(currVal);
  } else {
  	for (var i = 0; i < newArr.length; i++) {
    	if (currVal > newArr[i]) {
      	newArr.splice(0, i, currVal);
        break;
      }
    }
  }
  if (index === arr.length - 1) {
  	return newArr;
  }
  return getFlatArray(arr, index + 1, newArr);
}

function myfunction(arr) {
	
	let outputArr = getSortedArray(getFlatArray(arr));

return outputArr;

}

var sampleArr1 = [5, 10, 11, [2, 8], [12, 1, 4], [9, [5,4, 12]], 17];
console.log(myfunction(sampleArr1));