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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

Write a JavaScript program to get the lowest index at which value should be inserted into array in order to maintain its sort 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 
const sortedIndex = (arr, n) => {
  const isDescending = arr[0] > arr[arr.length - 1];
  const index = arr.findIndex(el => (isDescending ? n >= el : n <= el));
  return index === -1 ? arr.length : index;
};

console.log(sortedIndex([5, 3, 2, 1], 4));
console.log(sortedIndex([30, 50], 40));

Sample Output:

1
1

Flowchart:

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

Live Demo:

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


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JavaScript: Tips of the Day

How to remove a specific item from an array?

Find the index of the array element you want to remove using indexOf, and then remove that index with splice.

The splice() method changes the contents of an array by removing existing elements and/or adding new elements.

const array = [2, 5, 9];

console.log(array);

const index = array.indexOf(5);
if (index > -1) {
  array.splice(index, 1);
}

// array = [2, 9]
console.log(array);

The second parameter of splice is the number of elements to remove. Note that splice modifies the array in place and returns a new array containing the elements that have been removed.

For the reason of completeness, here are functions. The first function removes only a single occurrence (i.e. removing the first match of 5 from [2,5,9,1,5,8,5]), while the second function removes all occurrences:

function removeItemOnce(arr, value) {
  var index = arr.indexOf(value);
  if (index > -1) {
    arr.splice(index, 1);
  }
  return arr;
}

function removeItemAll(arr, value) {
  var i = 0;
  while (i < arr.length) {
    if (arr[i] === value) {
      arr.splice(i, 1);
    } else {
      ++i;
    }
  }
  return arr;
}
//Usage
console.log(removeItemOnce([2,5,9,1,5,8,5], 5))
console.log(removeItemAll([2,5,9,1,5,8,5], 5))

Ref: https://bit.ly/2N9nKRp