Percentile of Matches

Introduction

In this lab, we will explore the concept of calculating the percentile of matches in an array using JavaScript. Through the use of the Array.prototype.reduce() method, we will develop a function that can determine the percentage of numbers in an array that are less than or equal to a given value. This lab will help to reinforce your understanding of JavaScript array methods and their practical applications.

Skills Graph

Calculating Percentile of Matches

To calculate the percentile of matches in the given array below or equal to a given value, follow these steps:

1. Open the Terminal/SSH and type node to start coding practice.
2. Use the Array.prototype.reduce() method to calculate the number of values below the given value and the number of values equal to the given value.
3. Apply the percentile formula to obtain the percentage of matches.
4. Here's an example code snippet:

const percentile = (arr, val) =>
  (100 *
    arr.reduce(
      (acc, v) => acc + (v < val ? 1 : 0) + (v === val ? 0.5 : 0),
      0
    )) /
  arr.length;

5. To test the function, use this example code:

percentile([1, 2, 3, 4, 5, 6, 7, 8, 9, 10], 6); // Output: 55

This function will output the percentage of matches in the given array that are less than or equal to the given value.

Summary

Congratulations! You have completed the Percentile of Matches lab. You can practice more labs in LabEx to improve your skills.