Master the JavaScript interview with expertly curated questions and solutions. Strategies developed by FAANG engineers help you prep faster, boost confidence, and refine your problem-solving skills.

Master the JavaScript interview by practicing 20 carefully curated interview questions and solutions. These problems will provide the tools you need to tackle any question you find in an interview. Allow ~1 hour per question.

Most questions have multiple solutions presented. All solutions are thoroughly explained and time and space complexity are discussed. A passing familiarity with these ideas is expected. You'll learn how to tackle different types of problems so you can proceed with confidence in your interviews.

These questions go beyond the common problems that we've all seen. FizzBuzz and bubble sort? We start past those.

We'll discuss how to refine algorithms. We'll go over clever, advanced ways of manipulating data that interviewers are looking for. You'll walk away more skilled and confident in your problem solving and interviewing abilities.

This course is taught in ES2015.

Master the JavaScript Interview

# Highest Frequency

## Instructions

Write a function that takes an array of strings and returns the most commonly occurring string in that array.

If there are multiple strings with the same high frequency, return the one that finishes its occurrences first, while going left to right through the array.

**Input**: Array of Strings

**Output**: String

---

function highestFrequency(strings) {
    // Your code here
}

## How it Works

### Variables

The three variables declared at the top of the function are meant to keep track of data throughout the loop below. `frequencies` will contain data for every string that we process at every iteration. The keys will be the strings we process and those keys' values will be their frequency.

### Counting Frequency

`maxFrequency` and `mostFrequentString` will be maintained across iterations, updating when needed.

In the loop, we first check if we've already come across the string we're currently working with. If so, it already exists in our `frequencies` object and we can increment its value.

If we haven't come across it yet, we'll insert it into our object and give it a value of `1`.

### Keeping it Current

After that, on line 15, we're checking to see if the value we just updated or inserted into `frequencies` is greater than the largest frequency we've seen so far. If so, we update both the highest frequency and most frequent string.

After processing the whole array, `mostFrequentString` will contain the correct value and we can return it.

In this problem, we'll learn how to keep a count of values as we go through an array. From that data, we'll return the most common string in the array.

Introduction

Strings & Arrays

Advanced Strings & Arrays

Algorithms & Data Structures

JavaScript Mastery

Conclusion

Highest Frequency

Highest Frequency

Instructions