Where do I Belong - JavaScript Solution & Walkthrough

14/16 Where do I Belong

Return the lowest index at which a value (second argument) should be inserted into an array (first argument) once it has been sorted. The returned value should be a number.

For example, getIndexToIns([1,2,3,4], 1.5) should return 1 because it is greater than 1 (index 0), but less than 2 (index 1).

Likewise, getIndexToIns([20,3,5], 19) should return 2 because once the array has been sorted it will look like [3,5,20] and 19 is less than 20 (index 2) and greater than 5 (index 1).

function getIndexToIns(arr, num) {

  return num;
}

getIndexToIns([40, 60], 50);

Credit: FreeCodeCamp.org

Understanding the Challenge

For this challenge, you are to complete the getIndexToIn function. This function takes an array arr as first argument and a number num as second argument.

Your task is to find the lowest possible index num at which num can be insert into the array when it has been sorted. We are provided with 2 examples in the problem description.

Pseudocode

Given an array and an index number
  Update the array by inserting the number into the arry
  Sort the updated array
  Find the index of the number in the sorted array
return the index of the number.

Solving the Challenge

First, we need to update the arr by adding num to it. To add an element to an array, we can use the .push() method. This will add the number to the end of the array.

arr.push(num)
console.log(arr) // [ 40, 60, 50 ]

In the given example, the initial array is [40, 60]. Using the .push() method adds num which is 50 to the end of the array.

Next, we sort the array. We are not told specifically in challenge description how the sorting is to be done. However, looking at test cases provided, all of them were sorted in ascending order. Thus, its safe to assume that the function should do the sorting in ascending order. We can use the .sort() method to sort the array as follows;

arr.sort((a, b) => a - b)
console.log(arr) // [40, 50, 60]

We can now use the indexOf() method to find the index of num. We'll save the results in a variable. Let's call the variable indexOfNum.

const indexOfNum = arr.indexOf(num)
console.log(indexOfNum) // 1

Finally we return indexOfNum. Our function is now complete.

return index(indexOfNum)

Final Solution

function getIndexToIns(arr, num) {
  arr.push(num)
  arr.sort((a, b) => a - b)
  const indexOfNum = arr.indexOf(num)
  return indexOfNum;
}

getIndexToIns([40, 60], 50); // 1

Congratulations!

You just cracked the 14th challenge in this series.

Cheers and happy coding!