Convert String to Pascal Case

Introduction

In this lab, we will learn how to convert strings to Pascal case using JavaScript. Pascal case is a naming convention commonly used in programming where each word in a compound word begins with an uppercase letter, with no spaces or separators between words. For example, "hello world" becomes "HelloWorld" in Pascal case.

Throughout this lab, we will explore various JavaScript string manipulation methods and regular expressions to create a robust function that can convert any string to Pascal case, regardless of its original format.

Skills Graph

Understanding Pascal Case and Setting Up the Environment

Pascal case is a naming convention where:

• The first letter of each word is capitalized
• No spaces, hyphens, or underscores are used between words
• All other letters are lowercase

For example:

• "hello world" → "HelloWorld"
• "user_name" → "UserName"
• "first-name" → "FirstName"

Let's start by setting up our development environment.

1. Open the Terminal from the WebIDE interface by clicking on "Terminal" in the top menu bar.

2. Start a Node.js interactive session by typing the following command in the Terminal and pressing Enter:

node

You should see the Node.js prompt (>) appear, indicating that you are now in the Node.js interactive environment.

3. Let's try a simple string manipulation to get warmed up. Type the following code at the Node.js prompt:

let name = "john doe";
let capitalizedFirstLetter = name.charAt(0).toUpperCase() + name.slice(1);
console.log(capitalizedFirstLetter);

The output should be:

John doe

This simple example demonstrates how to capitalize the first letter of a string. We used:

• charAt(0) to get the first character
• toUpperCase() to convert it to uppercase
• slice(1) to get the rest of the string
• Concatenation with + to combine them

These string methods will be helpful as we build our Pascal case converter.

Working with Regular Expressions for Word Splitting

To convert a string to Pascal case, the first step is to split the string into individual words. We can use regular expressions (regex) to identify word boundaries regardless of the delimiter used (spaces, hyphens, underscores, etc.).

In JavaScript, regular expressions are enclosed between forward slashes (/pattern/). Let's explore how to use regex to split a string into words.

1. In your Node.js session, let's try a simple example first. Type the following code:

let str = "hello_world-example";
let words = str.split(/[-_]/);
console.log(words);

The output should be:

[ 'hello', 'world', 'example' ]

This regex /[-_]/ matches either a hyphen or an underscore, and split() uses these matches as separators.

2. Now, let's try a more complex string and regex. Type:

let complexStr = "hello_WORLD-example phrase";
let regex =
  /[A-Z]{2,}(?=[A-Z][a-z]+[0-9]*|\b)|[A-Z]?[a-z]+[0-9]*|[A-Z]|[0-9]+/g;
let matches = complexStr.match(regex);
console.log(matches);

The output should be:

[ 'hello', 'WORLD', 'example', 'phrase' ]

Let's break down this regex:

• /[A-Z]{2,}(?=[A-Z][a-z]+[0-9]*|\b)/: Matches uppercase letter sequences
• /[A-Z]?[a-z]+[0-9]*/: Matches words that may begin with an uppercase letter
• /[A-Z]/: Matches single uppercase letters
• /[0-9]+/: Matches number sequences
• The g flag makes the matching global (finds all matches)

The match() method returns an array of all matches found in the string. This will be essential for our Pascal case converter since it can identify words in almost any format.

Capitalizing Each Word

Now that we can split a string into words, we need to capitalize the first letter of each word and make the rest lowercase. Let's implement this functionality.

1. In your Node.js session, let's write a function to capitalize a single word. Type:

function capitalizeWord(word) {
  return word.charAt(0).toUpperCase() + word.slice(1).toLowerCase();
}

// Test with a few examples
console.log(capitalizeWord("hello"));
console.log(capitalizeWord("WORLD"));
console.log(capitalizeWord("javaScript"));

The output should be:

Hello
World
Javascript

2. Now, let's apply this function to an array of words using the map() method. Type:

let words = ["hello", "WORLD", "javaScript"];
let capitalizedWords = words.map((word) => capitalizeWord(word));
console.log(capitalizedWords);

The output should be:

[ 'Hello', 'World', 'Javascript' ]

The map() method creates a new array by applying a function to each element of the original array. In this case, we're applying our capitalizeWord function to each word.

3. Finally, let's join the capitalized words together to form a Pascal case string:

let pascalCase = capitalizedWords.join("");
console.log(pascalCase);

The output should be:

HelloWorldJavascript

The join("") method combines all elements of an array into a single string, using the provided delimiter (an empty string in this case) between each element.

These steps demonstrate the core process of converting a string to Pascal case:

1. Split the string into words
2. Capitalize each word
3. Join the words without any separators

Creating the Complete toPascalCase Function

Now that we understand all the components needed, let's create a complete toPascalCase function that can handle any input string.

1. Let's create a JavaScript file to save our function. Exit your Node.js session by pressing Ctrl+C twice or typing .exit.

2. In the WebIDE, create a new file by clicking "File" > "New File" in the top menu.

3. Save the file as pascalCase.js in the /home/labex/project directory.

4. Copy and paste the following code into the editor:

/**
 * Converts a string to Pascal case.
 * @param {string} str - The input string to convert.
 * @returns {string} The Pascal cased string.
 */
function toPascalCase(str) {
  // Use regex to match words regardless of delimiter
  const words = str.match(
    /[A-Z]{2,}(?=[A-Z][a-z]+[0-9]*|\b)|[A-Z]?[a-z]+[0-9]*|[A-Z]|[0-9]+/g
  );

  // If no words are found, return an empty string
  if (!words) {
    return "";
  }

  // Capitalize each word and join them
  return words
    .map((word) => word.charAt(0).toUpperCase() + word.slice(1).toLowerCase())
    .join("");
}

// Test cases
console.log(toPascalCase("hello world")); // "HelloWorld"
console.log(toPascalCase("some_database_field_name")); // "SomeDatabaseFieldName"
console.log(toPascalCase("Some label that needs to be pascalized")); // "SomeLabelThatNeedsToBePascalized"
console.log(toPascalCase("some-javascript-property")); // "SomeJavascriptProperty"
console.log(
  toPascalCase("some-mixed_string with spaces_underscores-and-hyphens")
); // "SomeMixedStringWithSpacesUnderscoresAndHyphens"

5. Save the file by pressing Ctrl+S or selecting "File" > "Save" from the menu.

6. Run the file using Node.js by opening the Terminal and typing:

node pascalCase.js

You should see the following output:

HelloWorld
SomeDatabaseFieldName
SomeLabelThatNeedsToBePascalized
SomeJavascriptProperty
SomeMixedStringWithSpacesUnderscoresAndHyphens

Our toPascalCase function is now working correctly. Let's review how it works:

1. We use a regular expression to match words in the input string, regardless of the delimiters used.
2. We check if any words were found. If not, we return an empty string.
3. We use map() to capitalize each word and join('') to combine them without separators.
4. The result is a Pascal-cased string where each word begins with an uppercase letter and the rest are lowercase.

Enhancing and Using the Pascal Case Function

Now that we have a working toPascalCase function, let's enhance it with additional features and learn how to use it in a practical way.

1. Open your pascalCase.js file in the WebIDE.

2. Let's modify the function to handle edge cases better. Replace the existing code with:

/**
 * Converts a string to Pascal case.
 * @param {string} str - The input string to convert.
 * @returns {string} The Pascal cased string.
 */
function toPascalCase(str) {
  // Handle edge cases
  if (!str) return "";
  if (typeof str !== "string") return "";

  // Use regex to match words regardless of delimiter
  const words = str.match(
    /[A-Z]{2,}(?=[A-Z][a-z]+[0-9]*|\b)|[A-Z]?[a-z]+[0-9]*|[A-Z]|[0-9]+/g
  );

  // If no words are found, return an empty string
  if (!words) {
    return "";
  }

  // Capitalize each word and join them
  return words
    .map((word) => word.charAt(0).toUpperCase() + word.slice(1).toLowerCase())
    .join("");
}

// Test cases including edge cases
console.log(toPascalCase("hello world")); // "HelloWorld"
console.log(toPascalCase("")); // ""
console.log(toPascalCase(null)); // ""
console.log(toPascalCase("123_abc")); // "123Abc"
console.log(toPascalCase("UPPER_CASE_EXAMPLE")); // "UpperCaseExample"
console.log(
  toPascalCase("some-mixed_string with spaces_underscores-and-hyphens")
); // "SomeMixedStringWithSpacesUnderscoresAndHyphens"

// Create a reusable utility module
module.exports = { toPascalCase };

3. Save the file by pressing Ctrl+S.

4. Now, let's create a new file to demonstrate how to use our function as a utility in another file. Create a new file by clicking "File" > "New File" in the top menu.

5. Save this file as useCase.js in the /home/labex/project directory.

6. Add the following code to useCase.js:

// Import the toPascalCase function from our utility file
const { toPascalCase } = require("./pascalCase");

// Example: Converting database field names to JavaScript variable names
const databaseFields = [
  "user_id",
  "first_name",
  "last_name",
  "email_address",
  "date_of_birth"
];

// Convert each field name to Pascal case
const javaScriptVariables = databaseFields.map((field) => toPascalCase(field));

// Display the results
console.log("Database Fields:");
console.log(databaseFields);
console.log("\nJavaScript Variables (Pascal Case):");
console.log(javaScriptVariables);

// Example: Creating a class name from a description
const description = "user account manager";
const className = toPascalCase(description);
console.log(`\nClass name created from "${description}": ${className}`);

7. Save the file by pressing Ctrl+S.

8. Run the new file using Node.js. In the Terminal, type:

node useCase.js

You should see output similar to:

Database Fields:
[ 'user_id', 'first_name', 'last_name', 'email_address', 'date_of_birth' ]

JavaScript Variables (Pascal Case):
[ 'UserId', 'FirstName', 'LastName', 'EmailAddress', 'DateOfBirth' ]

Class name created from "user account manager": UserAccountManager

This demonstrates a practical use of the toPascalCase function for converting database field names to JavaScript variable names and creating class names from descriptions.

Note that we also added:

1. Error handling for null, undefined, or non-string inputs
2. Module exports so the function can be imported into other files
3. A real-world example of using the function

These enhancements make our toPascalCase function more robust and usable in real JavaScript applications.

Summary

In this lab, you've learned how to convert strings to Pascal case in JavaScript. Here's what you've accomplished:

1. Understood the concept of Pascal case and its applications in programming
2. Learned how to use regular expressions to split strings into words regardless of delimiters
3. Applied string manipulation methods such as charAt(), slice(), toUpperCase(), and toLowerCase()
4. Created a robust toPascalCase function that handles various input formats
5. Enhanced the function with error handling and exported it as a module
6. Applied the function to practical use cases like converting database field names to JavaScript variables

These skills are useful in many programming scenarios, such as:

• Converting between different naming conventions
• Processing user input into standardized formats
• Working with data from different sources
• Creating consistent naming in your code

You can continue to build on these skills by exploring other string manipulation techniques and applying them to your own projects.