JavaScript: Capitalize the first letter of a string

JavaScript fundamental (ES6 Syntax): Exercise-263 with Solution

Capitalize First Letter

Write a JavaScript program to capitalize the first letter of a string.

• Use array destructuring and String.prototype.toUpperCase() to capitalize the first letter of the string.
• Use Array.prototype.join('') to combine the capitalized first with the ...rest of the characters.
• Omit the lowerRest argument to keep the rest of the string intact, or set it to true to convert to lowercase.

Sample Solution:

JavaScript Code:

// Define a function 'capitalize' to capitalize the first letter of a string
// and optionally lowercase the rest of the string
const capitalize = ([first, ...rest], lowerRest = false) =>
  // Convert the first character to uppercase and concatenate it with the rest of the string
  first.toUpperCase() + 
  // If 'lowerRest' is true, join the remaining characters and convert them to lowercase,
  // otherwise, join the remaining characters as they are
  (lowerRest ? rest.join('').toLowerCase() : rest.join(''));

// Test the function with different inputs
console.log(capitalize('fooBar')); // Output: "FooBar"
console.log(capitalize('fooBar', true)); // Output: "Foobar"

Output:

FooBar
Foobar

Visual Presentation:

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-263-1 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript program that capitalizes the first letter of a given string while leaving the rest unchanged.
• Write a JavaScript function that trims a string and then converts only its first character to uppercase.
• Write a JavaScript program that uses regular expressions to identify and capitalize the first letter of a string.
• Write a JavaScript function that capitalizes the first letter of a sentence and returns the modified string.

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