Replace all chars after - in string to uppercase in JS

I have function

firstLetterUppercase(str: string) {
    let splitStr = str.toLowerCase().split(' ');
    for (let i = 0; i < splitStr.length; i++) {
      splitStr[i] = splitStr[i].charAt(0).toUpperCase() + splitStr[i].substring(1);
    }
    return splitStr.join(' ');
  }

It's work fine for string: Warszawa, Krakow, Bielsko - Biala etc.

I need change it to string 'Bielsko-biala'.
(i need first char after '-' uppercase too).

How can i make it?

Please help me

You can use a regular expression and the replace() method to find and replace the lowercase letters after a dash with their uppercase counterparts.

function firstLetterUppercase(str: string) {
  let splitStr = str.toLowerCase().split(" ");
  for (let i = 0; i < splitStr.length; i++) {
    splitStr[i] =
      splitStr[i].charAt(0).toUpperCase() + splitStr[i].substring(1);
    splitStr[i] = splitStr[i].replace(/-([a-z])/g, (match) =>
      match.toUpperCase()
    );
  }
  return splitStr.join(" ");
}

Here is the updated code that will work for 'Bielsko-biala'.
In the modified function, I have added a conditional statement to check if the current word contains a hyphen ('-'). If it does, I locate the index of the hyphen using indexOf('-'). Then, it capitalizes the letter immediately after the hyphen by concatenating the relevant portions of the string with their capitalized counterparts.

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

function firstLetterUppercase(str) {
  let splitStr = str.toLowerCase().split(' ');

  for (let i = 0; i < splitStr.length; i++) {
    if (splitStr[i].includes('-')) {
      let hyphenIndex = splitStr[i].indexOf('-');
      splitStr[i] =
        splitStr[i].charAt(0).toUpperCase() +
        splitStr[i].substring(1, hyphenIndex + 1) +
        splitStr[i].charAt(hyphenIndex + 1).toUpperCase() +
        splitStr[i].substring(hyphenIndex + 2);
    } else {
      splitStr[i] = splitStr[i].charAt(0).toUpperCase() + splitStr[i].substring(1);
    }
  }

  return splitStr.join(' ');
}

console.log(firstLetterUppercase('Bielsko-biala'))

<!-- end snippet -->

One way of doing it can be:

function firstLetterUppercase(str) {
  let splitStr = str.toLowerCase().split(' ');
  for (let i = 0; i < splitStr.length; i++) {
    splitStr[i] = splitStr[i].charAt(0).toUpperCase() + splitStr[i].substring(1);
  }

  //Added code
  let result = splitStr.join(' ');
  result = result.replace(/-([a-z])/g, function(match, group1) {
    return '-' + group1.toUpperCase();
  });

  return result;
}

If you want to "replace" "all" the "characters" starting after "word border", with their "Upper case"
the easiest way would be using regular expressions:

/**
 * `replaceAll`(`g` regex flag) characters of any type (`.`)
 * after word border (`\b`) with their `toUpperCase`
 */
function firstLetterUppercase(str) {
  return str.replaceAll(/\b./g, c => c.toUpperCase())
}