schnippets/typescript_utils/title-case.ts

// Standalone function
export const toTitleCase = function(str: string): string {
  str = str.replace(/([^\W_]+[^\s-]*) */g, function(txt) {
    return txt.charAt(0).toUpperCase() + txt.substr(1).toLowerCase();
  });

  // Certain minor words should be left lowercase unless
  // they are the first or last words in the string
  const lowers = [
    'A',
    'An',
    'And',
    'As',
    'At',
    'But',
    'By',
    'For',
    'From',
    'In',
    'Into',
    'Is',
    'Near',
    'Nor',
    'Of',
    'On',
    'Onto',
    'Or',
    'The',
    'To',
    'With',
  ];
  const uppers = ['Id', 'Tv'];

  for (let i = 0; i < lowers.length; i++)
    str = str.replace(new RegExp('\\s' + lowers[i] + '\\s', 'g'), function(txt) {
      return txt.toLowerCase();
    });

  // Certain words such as initialisms or acronyms should be left uppercase
  for (let i = 0; i < uppers.length; i++)
    str = str.replace(new RegExp('\\b' + uppers[i] + '\\b', 'g'), uppers[i].toUpperCase());

  return str;
};

// Prototype onto String so any string gets "".toTitleCase()
String.prototype.toTitleCase = function() {
  let str = this.replace(/([^\W_]+[^\s-]*) */g, function(txt) {
    return txt.charAt(0).toUpperCase() + txt.substr(1).toLowerCase();
  });

  // Certain minor words should be left lowercase unless
  // they are the first or last words in the string
  const lowers = [
    'A',
    'An',
    'And',
    'As',
    'At',
    'But',
    'By',
    'For',
    'From',
    'In',
    'Into',
    'Is',
    'Near',
    'Nor',
    'Of',
    'On',
    'Onto',
    'Or',
    'The',
    'To',
    'With',
  ];
  const uppers = ['Id', 'Tv'];

  for (let i = 0; i < lowers.length; i++)
    str = str.replace(new RegExp('\\s' + lowers[i] + '\\s', 'g'), function(txt) {
      return txt.toLowerCase();
    });

  // Certain words such as initialisms or acronyms should be left uppercase
  for (let i = 0; i < uppers.length; i++)
    str = str.replace(new RegExp('\\b' + uppers[i] + '\\b', 'g'), uppers[i].toUpperCase());

  return str;
};