Capitalizes 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 of the characters.
  • Omit the lowerRest argument to keep the rest of the string intact, or set it to true to convert to lowercase.
const capitalize = ([first,], lowerRest = false) =>
  first.toUpperCase() +
  (lowerRest ? rest.join('').toLowerCase() : rest.join(''));
capitalize('fooBar'); // 'FooBar'
capitalize('fooBar', true); // 'Foobar'