Función para capitalizar strings

string.capitalize.js

function capitalize() {
  try {
    if (typeof this !== 'string') throw new Error('Capitalize must be used in a String value.');
    const str = this.split(' ')
                    .map(v => {
                      return v.split('')
                              .map((v,i) => (i === 0) ? v.toUpperCase() : v)
                              .join('');
                    }).join(' ');
    return str;
  } catch (error) {
    return error;
  }
}