JavaScript - How to Make First Letter of a String Uppercase?

Here are the different approaches to make the first letter of a string uppercase in JavaScript.

1. Using charAt() with slice() Method (Most Common)

The combination of charAt() and slice() is the simplest and widely used way to capitalize the first letter of a string.

const s1 = "javaScript";
const s2 = s1.charAt(0).toUpperCase() + s1.slice(1);
console.log(s2);

JavaScript

• charAt(0): Extracts the first character of the string.
• toUpperCase(): Converts the first character to uppercase.
• slice(1): Extracts the rest of the string starting from the second character.

2. Using JavaScript replace() Method

The replace() method with a regular expression provides a clean and flexible way to capitalize the first letter.

const s1 = "javaScript";
const s2 = s1.replace(/^./, char => char.toUpperCase());
console.log(s2);

JavaScript

• /^./: Matches the first character of the string (. represents any character, and ^ anchors it to the start).
• char => char.toUpperCase(): Transforms the matched character to uppercase.

3. Using Template Literals and slice() Method

If you prefer using modern JavaScript features like template literals, this approach is concise and readable.

const s1 = "javaScript";
const s2 = `${s1.charAt(0).toUpperCase()}${s1.slice(1)}`;
console.log(s2);

JavaScript

• Template literals (${}) are used for string interpolation.
• Combines the uppercase first letter and the remaining substring directly.

Which One to Choose?

• The charAt() with slice() method is the simplest and most commonly used way to capitalize the first letter of a string.
• replace() with regular expressions offers a powerful alternative, especially for advanced use cases.