JavaScript: Get the highest index at which value should be inserted into array in order to maintain its sort order

JavaScript fundamental (ES6 Syntax): Exercise-141 with Solution

Highest Index for Sorted Insertion

Write a JavaScript program to get the highest index at which value should be inserted into an array in order 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:

//#Source https://bit.ly/2neWfJ2 

// Define the 'sortedLastIndex' function
const sortedLastIndex = (arr, n) => {
  // Determine if the array is sorted in descending order
  const isDescending = arr[0] > arr[arr.length - 1];
  // Find the index where 'n' should be inserted into the sorted array
  const index = arr
    .reverse() // Reverse the array to search from the end
    .findIndex(el => (isDescending ? n <= el : n >= el)); // Find the index based on sorting order
  // Return the index after adjusting for the reversed array and considering array length
  return index === -1 ? 0 : arr.length - index;
};

// Test the 'sortedLastIndex' function
console.log(sortedLastIndex([10, 20, 30, 30, 40], 30)); // Output: 4

Output:

4

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-141-1 by w3resource (@w3resource) on CodePen.

Improve this sample solution and post your code through Disqus

Previous: Write a JavaScript program to get the highest index at which value should be inserted into array in order to maintain its sort order, based on a provided iterator function.
Next: Write a JavaScript program to get the lowest index at which value should be inserted into array in order to maintain its sort order.