Javascript:Check if Array is sorted

Problem Statement:

Given an array of number find out if it is sorted and in which order.

E.g.If input is [ 22, 25, -6, 8, 67, 100 ] then output should be not sorted.

If input is [ -6, 8, 22, 25, 67, 100 ] then output should be sorted in ascending order.

If input is [ 100, 67, 25, 22, 2 ] then output should be sorted in descending order.

Solution:

function isArraySorted(arr, sortDirection = "asc") {

//create an array with [0,1,2,..,length-1]

let rangeArray = Array.from(Array(arr.length).keys());

//ascending order sorted

if (sortDirection == "asc") {

//in ascending order previous element is lesser than next element otherwise not sorted

let isSortedInAscendingOrder = rangeArray.reduce((accumulator, element) => {

if (element < arr.length && arr[element] > arr[element + 1]) {

accumulator = false;

}

return accumulator;

}, true);

return isSortedInAscendingOrder;

}

//descending order sorted

if (sortDirection == "desc") {

let isSortedInDescendingOrder = rangeArray.reduce(

(accumulator, element) => {

//in descending order previous element is greater than next element otherwise not sorted

if (element < arr.length && arr[element] < arr[element + 1]) {

accumulator = false;

}

return accumulator;

},

true

);

return isSortedInDescendingOrder;

}

return false;

}

//Driver code

//not sorted array as input

let notSorted = [22, 25, -6, 8, 67, 100];

console.log("Not Sorted Array as Input:", notSorted);

let notSortedisAscendingSorted = isArraySorted(notSorted, "asc");

console.log("Array is sorted in Ascending Order:", notSortedisAscendingSorted);

let notSortedIsDescendingSorted = isArraySorted(notSorted, "desc");

console.log("Array is sorted in Descending Order:", notSortedisAscendingSorted);

console.log('------Ascending Sorted Array As Input-------------')

//ascending sorted array as input

let ascendingSorted = [-6, 8, 22, 25, 67, 100];

console.log("Ascending Sorted Array as Input:", ascendingSorted);

let ascendingSortedisAscendingSorted = isArraySorted(ascendingSorted, "asc");

console.log(

"Array is sorted in Ascending Order:",

ascendingSortedisAscendingSorted

);

let ascendingSortedIsDescendingSorted = isArraySorted(ascendingSorted, "desc");

console.log(

"Array is sorted in Descending Order:",

ascendingSortedIsDescendingSorted

);

console.log('------Descending Sorted Array As Input-------------')

//descending sorted array as input

let descendingSorted = [100, 67, 25, 22, 8 - 6];

console.log("Descending Sorted Array as Input:", descendingSorted);

let descendingSortedisAscendingSorted = isArraySorted(descendingSorted, "asc");

console.log(

"Array is sorted in Ascending Order:",

descendingSortedisAscendingSorted

);

let descendingSortedIsDescendingSorted = isArraySorted(descendingSorted, "desc");

console.log(

"Array is sorted in Descending Order:",

descendingSortedIsDescendingSorted

);

Output:

Not Sorted Array as Input: [ 22, 25, -6, 8, 67, 100 ]

Array is sorted in Ascending Order: false

Array is sorted in Descending Order: false

------Ascending Sorted Array As Input-------------

Ascending Sorted Array as Input: [ -6, 8, 22, 25, 67, 100 ]

Array is sorted in Ascending Order: true

Array is sorted in Descending Order: false

------Descending Sorted Array As Input-------------

Descending Sorted Array as Input: [ 100, 67, 25, 22, 2 ]

Array is sorted in Ascending Order: false

Array is sorted in Descending Order: true

Note:

If array has only one element or all elements are same then it can be

considered as sorted in both ascending & descending order.