JavaScript Sorting Algorithm: Sorted last index

JavaScript Sorting Algorithm: Exercise-23 with Solution

Find Highest Insert Index (Array)

Write a JavaScript program to find the highest index at which a value should be inserted into an array to maintain its sort order.

• 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 sortedLastIndex = (arr, n) => {
  const isDescending = arr[0] > arr[arr.length - 1];
  const index = arr
    .reverse()
    .findIndex(el => (isDescending ? n <= el : n >= el));
  return index === -1 ? 0 : arr.length - index;
}; 
console.log(sortedLastIndex([10, 20, 30, 30, 40], 30));

Sample Output:

4

Flowchart:

Live Demo:

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

For more Practice: Solve these Related Problems:

• Write a JavaScript function that finds the highest index where a given value can be inserted in a sorted array.
• Write a JavaScript function that uses reverse iteration to determine the correct insertion index for duplicate values.
• Write a JavaScript function that validates the input array and returns the highest valid insertion index.
• Write a JavaScript function that simulates inserting the value at the computed index and checks if the order remains sorted.

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