JavaScript Searching and Sorting Algorithm: Sorted IndexBy

Last update on May 30 2022 10:06:43 (UTC/GMT +8 hours)

JavaScript Searching and Sorting Algorithm: Exercise-20 with Solution

Write a JavaScript program to find the lowest index at which a value should be inserted into an array in order to maintain its sorting order, based on the provided iterator function.

Loosely check if the array is sorted in descending order.
Use Array.prototype.findIndex() to find the appropriate index where the element should be inserted, based on the iterator function fn.

Sample Solution:

JavaScript Code:

const sortedIndexBy = (arr, n, fn) => {
  const isDescending = fn(arr[0]) > fn(arr[arr.length - 1]);
  const val = fn(n);
  const index = arr.findIndex(el =>
    isDescending ? val >= fn(el) : val <= fn(el)
  );
  return index === -1 ? arr.length : index;
};

console.log(sortedIndexBy([{ x: 4 }, { x: 5 }], { x: 4 }, o => o.x));

Sample Output:

Flowchart:

JavaScript Searching and Sorting Algorithm Exercises: Sorted IndexBy.

Live Demo:

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

Improve this sample solution and post your code through Disqus

Previous: Write a JavaScript program to sort the characters in a string alphabetically.
Next: Write a JavaScript program to Finds the index of a given element in a sorted array using the binary search algorithm.

What is the difficulty level of this exercise?

Test your Programming skills with w3resource's quiz.

JavaScript: Tips of the Day

How to insert an item into an array at a specific index (JavaScript)?

What you want is the splice function on the native array object.

arr.splice(index, 0, item); will insert item into arr at the specified index (deleting 0 items first, that is, it's just an insert). In this example we will create an array and add an element to it into index 2:

var arr = [];
arr[0] = "Jani";
arr[1] = "Hege";
arr[2] = "Stale";
arr[3] = "Kai Jim";
arr[4] = "Borge";

console.log(arr.join());
arr.splice(2, 0, "Lene");
console.log(arr.join());

Ref: https://bit.ly/2BXbp04