Camel Case - FreeCodeCamp Daily Challenge

Introduction

The “Camel Case” challenge from FreeCodeCamp asks us to transform a string into camel case format, a convention widely used in programming for naming variables and functions. This exercise is perfect for practicing string manipulation and regular expressions in JavaScript.

Problem Statement

Given a string, return its camel case version following these rules:

• Words are separated by one or more of the following characters: space ( ), hyphen (-), or underscore (_).
• Each subsequent word should start with an uppercase letter, the rest in lowercase.
• All separators must be removed.

Example:

• Input: "hello world" → Output: "helloWorld"
• Input: "secret agent-X" → Output: "secretAgentX"

Process Visualization

The process can be visualized as a flow of steps:

flowchart TD
    A[Input String] --> B[Split into words]
    B --> C[Normalize: lowercase]
    C --> D[Capitalize initial]
    D --> E[Concatenate]
    E --> F[Camel Case Result]

Approach & Analysis

Initial Observations

• Separators can be multiple and mixed.
• It’s important to remove empty words that arise from consecutive separators.

Strategy

1. Split the string into words using a regular expression that detects spaces, hyphens, and underscores.
2. Convert the first word to lowercase.
3. Capitalize the first letter of each subsequent word.
4. Concatenate all words.

Step-by-Step Implementation

function toCamelCase(s) {
  let words = s
    .toLowerCase()
    .split(/[\s-_]+/)
    .filter(Boolean)

  for (let i = 1; i < words.length; i++) {
    words[i] = words[i][0].toUpperCase() + words[i].slice(1)
  }

  return words.join('')
}

export default toCamelCase

Key point: Using filter(Boolean) removes empty words generated by consecutive separators.

Complexity Analysis

• Time: $O(n)$, where $n$ is the length of the string.
• Space: $O(n)$, for the list of words and the final result.

Test Cases and Edge Cases

toCamelCase('hello world') // "helloWorld"
toCamelCase('HELLO WORLD') // "helloWorld"
toCamelCase('secret agent-X') // "secretAgentX"
toCamelCase('FREE cODE cAMP') // "freeCodeCamp"
toCamelCase('ye old-_-sea faring_buccaneer_-_with a - peg__leg----and a_parrot_ _named- _squawk') // "yeOldSeaFaringBuccaneerWithAPegLegAndAParrotNamedSquawk"

Edge cases include empty strings, only separators, or special characters. The solution handles them correctly.

Alternatives and Optimizations

A more compact version using replace and a callback function:

function toCamelCase(s) {
  return s
    .toLowerCase()
    .replace(/[\s-_]+(.)/g, (match, group1) => group1.toUpperCase())
}

However, the original version is more readable and maintainable.

Reflections and Learnings

This problem is excellent for practicing:

• String manipulation
• Regular expressions
• Handling edge cases
• Complexity analysis

Resources and References

• Camel Case on Wikipedia
• String on MDN
• Regular Expressions in JavaScript