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

JavaScript fundamental (ES6 Syntax): Exercise-142 with Solution

Lowest Index for Sorted Insertion

Write a JavaScript program to get the lowest index at which values should be inserted into an array in order to maintain its sorting order.

Note: Check if the array is sorted in descending order (loosely).

• 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.

Sample Solution:

JavaScript Code:

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

// Define the 'sortedIndex' function
const sortedIndex = (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.findIndex(el => (isDescending ? n >= el : n <= el));
  // Return the index or the length of the array if 'n' is greater than all elements
  return index === -1 ? arr.length : index;
};

// Test the 'sortedIndex' function
console.log(sortedIndex([5, 3, 2, 1], 4)); // Output: 1
console.log(sortedIndex([30, 50], 40)); // Output: 1

Output:

1
1

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-142-1 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript program that finds the lowest index at which a value can be inserted into a sorted array while preserving order.
• Write a JavaScript function that iterates over a sorted array to return the first suitable insertion index for a given number.
• Write a JavaScript program that employs a binary search to efficiently find the lowest valid insertion index in an array.

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