L.toUpperCase()); } "I'm a little tea pot".match(/(^|\s)\S/g)//["I", " a", " l", " t", " p"]"> L.toUpperCase()); } "I'm a little tea pot".match(/(^|\s)\S/g)//["I", " a", " l", " t", " p"]"> L.toUpperCase()); } "I'm a little tea pot".match(/(^|\s)\S/g)//["I", " a", " l", " t", " p"]"> 
//use array
function titleCase(str) {
  let lowerCasewords = str.toLowerCase().split(' ')
  let titleCaseWords = lowerCasewords.map(word=> {
    return word.replace(word.charAt(0),word.charAt(0).toUpperCase())
  })
  return titleCaseWords.join(' ');
}
titleCase("I'm a little tea pot");

//use regex
function titleCase(str) {
	//每匹配一次，就替换一次，每次替换都调用函数
  return str.toLowerCase().replace(/(^|\\s)\\S/g, L => L.toUpperCase());
}
"I'm a little tea pot".match(/(^|\\s)\\S/g)//["I", " a", " l", " t", " p"]