JavaScript Sorting Algorithm: Check if a numeric array is sorted or not

JavaScript Sorting Algorithm: Exercise-24 with Solution

Write a JavaScript program to check if a numeric array is sorted or not.

• Loosely check if the array is sorted in descending order.
• Use Array.prototype.reverse() and Array.prototype.findIndex() to find the appropriate last index where the element should be inserted.

Sample Solution:

JavaScript Code:

const isSorted = arr => {
  if (arr.length <= 1) return 0;
  const direction = arr[1] - arr[0];
  for (let i = 2; i < arr.length; i++) {
    if ((arr[i] - arr[i - 1]) * direction < 0) return 0;
  }
  return Math.sign(direction);
};
console.log(isSorted([0, 1, 2, 2]));
console.log(isSorted([4, 3, 2]));
console.log(isSorted([4, 3, 5]));
console.log(isSorted([4]));

Sample Output:

1
-1
0
0

Flowchart:

Live Demo:

See the Pen javascript-common-editor by w3resource (@w3resource) on CodePen.

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