JavaScript Program to Convert String to Title Case

Use str.split(' ').map(word => word.charAt(0).toUpperCase() + word.slice(1).toLowerCase()).join(' ') to convert a string to title case in JavaScript.

Examples

Inputhello world

OutputHello World

InputjavaScript is fun

OutputJavascript Is Fun

Input multiple spaces here

OutputMultiple Spaces Here

How to Think About It

To convert a string to title case, split the string into words by spaces, then for each word, change the first letter to uppercase and the rest to lowercase, and finally join the words back with spaces.

Algorithm

1

Get the input string.

2

Split the string into an array of words using spaces.

3

For each word, convert the first character to uppercase and the rest to lowercase.

4

Join all the transformed words back into a single string with spaces.

5

Return the resulting title-cased string.

Code

javascript

function toTitleCase(str) {
  return str
    .split(' ')
    .filter(word => word.length > 0)
    .map(word => word.charAt(0).toUpperCase() + word.slice(1).toLowerCase())
    .join(' ');
}

console.log(toTitleCase('hello world'));
console.log(toTitleCase('javaScript is fun'));
console.log(toTitleCase('  multiple   spaces here '));

Output

Hello World
Javascript Is Fun
Multiple Spaces Here

Dry Run

Let's trace 'javaScript is fun' through the code

1

Split string

Split 'javaScript is fun' into ['javaScript', 'is', 'fun']

2

Filter empty words

No empty words to remove, array remains ['javaScript', 'is', 'fun']

3

Map each word

Transform each word: 'javaScript' -> 'Javascript' 'is' -> 'Is' 'fun' -> 'Fun'

4

Join words

Join ['Javascript', 'Is', 'Fun'] into 'Javascript Is Fun'

Original Word	Transformed Word
javaScript	Javascript
is	Is
fun	Fun

Why This Works

Step 1: Splitting the string

We split the string by spaces using split(' ') to get each word separately.

Step 2: Capitalizing each word

For each word, we take the first letter with charAt(0), convert it to uppercase, then add the rest of the word in lowercase with slice(1).toLowerCase().

Step 3: Joining words back

We join all the capitalized words back into one string with spaces using join(' ').

Alternative Approaches

Using Regular Expression

javascript

function toTitleCaseRegex(str) {
  return str.toLowerCase().replace(/\b\w/g, char => char.toUpperCase());
}

console.log(toTitleCaseRegex('hello world'));

This method uses regex to find word starts and capitalize them, which is concise but less explicit.

Using for loop

javascript

function toTitleCaseLoop(str) {
  const words = str.split(' ').filter(w => w.length > 0);
  let result = '';
  for (let i = 0; i < words.length; i++) {
    result += words[i].charAt(0).toUpperCase() + words[i].slice(1).toLowerCase();
    if (i < words.length - 1) result += ' ';
  }
  return result;
}

console.log(toTitleCaseLoop('hello world'));

This approach uses a loop instead of map, which some beginners find easier to understand.

Complexity: O(n) time, O(n) space

Time Complexity

The program processes each character once when splitting and mapping, so time grows linearly with string length.

Space Complexity

Extra space is used for the array of words and the new string, proportional to input size.

Which Approach is Fastest?

The regex method is concise and fast for typical strings, but the map method is clearer and easier to maintain.

Approach	Time	Space	Best For
Map with split	O(n)	O(n)	Readability and clarity
Regex replace	O(n)	O(n)	Concise code and speed
For loop	O(n)	O(n)	Beginners learning loops