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  3. Uppercase the First Character of a String in JavaScript or Node.js

Uppercase the First Character of a String in JavaScript or Node.js

Changing only the first character of a string value in JavaScript may happen when you scaffold files or code in your projects. You may want to ensure a specific casing for your method or class names. For example, you could ensure a class name always starts with an uppercase character.

This tutorial shows you how to uppercase the first character of a string.

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Capitalize the First Letter of a String in JavaScript

Uppercasing the first character in a string requires you to put some checks in place before accessing and changing the casing of letters.

At first, make sure you’re working on a string value. The typeof operator is fine for that check. We have a dedicated tutorial here at Future Studio on checking whether a given value is a string which you might check out, too.

Then, you need to detect whether the string is empty. If the string doesn’t have characters to uppercase, you can return the empty string and stop.

From here, you want to transform the first letter to uppercase and leave the rest “as is”. The rest is everything in the string starting from the second letter.

Here’s a ucFirst utility method accepting a string as an argument and returning the string with an uppercased first character:

/**
 * Uppercases the first character in the `string`.
 *
 * @param {String} string
 *
 * @returns {String}
 */
function ucFirst (string) {  
  if (!(typeof string !== 'string')) { 
    return ''
  }

  if (string.length === 0) {
    return ''
  }

  return string[0].toUpperCase() + string.slice(1)
}

Now you can use the created ucFirst function like this:

ucFirst()  
// ''

ucFirst('a')  
// 'A'

ucFirst('ABC')  
// 'ABC'

ucFirst('controller')  
// 'Controller'

ucFirst('future Studio')  
// 'Future Studio'

Use the @supercharge/strings Package

I’m the maintainer of the @supercharge/strings package providing convenient string utilities. The @supercharge/strings package comes with a handy Str#ucFirst method.

This ucFirst method uppercases the first character in a string and leaves the rest “as is”:

import { Str } from '@supercharge/string'

Str().ucFirst().get()  
// ''

Str('a').ucFirst().get()  
// 'A'

Str('ABC').ucFirst().get()  
// 'ABC'

Str('controller').ucFirst().get()  
// 'Controller'

Str('future Studio').ucFirst().get()  
// 'Future Studio'

Enjoy uppercasing the first character of a string!

Mentioned Resources

Marcus Pöhls

Marcus is a fullstack JS developer. He’s passionate about the hapi framework for Node.js and loves to build web apps and APIs. Creator of Futureflix and the “learn hapi” learning path.

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