function toTitleCase(str) {
  var strnew = "";
  var i = 0;

  for (i = 0; i < str.length; i++) {
    if (i == 0) {
      strnew = strnew + str[i].toUpperCase();
    } else if (i != 0 && str[i - 1] == " ") {
      strnew = strnew + str[i].toUpperCase();
    } else {
      strnew = strnew + str[i];
    }
  }

  alert(strnew);
}

toTitleCase("hello world how are u");

ES-6 way to get title case of a word or entire line.
ex. input = 'hEllo' --> result = 'Hello'
ex. input = 'heLLo woRLd' --> result = 'Hello World'

const getTitleCase = (str) => {
  if(str.toLowerCase().indexOf(' ') > 0) {
    return str.toLowerCase().split(' ').map((word) => {
      return word.replace(word[0], word[0].toUpperCase());
    }).join(' ');
  }
  else {
    return str.slice(0, 1).toUpperCase() + str.slice(1).toLowerCase();
  }
}

var toMatch = "john w. smith";
var result = toMatch.replace(/(\w)(\w*)/g, function (_, i, r) {
      return i.toUpperCase() + (r != null ? r : "");
    }
)

似乎有用… 用上面的测试，“快棕色的狐狸?/跳过/越过了……“C:/程序文件/某些供应商/他们的第二个应用程序/a file1.txt”。

如果你想要2Nd而不是2Nd，你可以更改为/([a-z])(\w*)/g。

第一种形式可以简化为:

function toTitleCase(toTransform) {
  return toTransform.replace(/\b([a-z])/g, function (_, initial) {
      return initial.toUpperCase();
  });
}

https://lodash.com/docs/4.17.11#capitalize

使用Lodash库!!更可靠的

_.capitalize('FRED'); => 'Fred'

这个解决方案将标点符号考虑到新句子中，处理引用，将小词转换为小写，忽略首字母缩写或全大写单词。

var stopWordsArray = new Array("a", "all", "am", "an", "and", "any", "are", "as", "at", "be", "but", "by", "can", "can't", "did", "didn't", "do", "does", "doesn't", "don't", "else", "for", "get", "gets", "go", "got", "had", "has", "he", "he's", "her", "here", "hers", "hi", "him", "his", "how", "i'd", "i'll", "i'm", "i've", "if", "in", "is", "isn't", "it", "it's", "its", "let", "let's", "may", "me", "my", "no", "of", "off", "on", "our", "ours", "she", "so", "than", "that", "that's", "thats", "the", "their", "theirs", "them", "then", "there", "there's", "these", "they", "they'd", "they'll", "they're", "they've", "this", "those", "to", "too", "try", "until", "us", "want", "wants", "was", "wasn't", "we", "we'd", "we'll", "we're", "we've", "well", "went", "were", "weren't", "what", "what's", "when", "where", "which", "who", "who's", "whose", "why", "will", "with", "won't", "would", "yes", "yet", "you", "you'd", "you'll", "you're", "you've", "your");

// Only significant words are transformed. Handles acronyms and punctuation
String.prototype.toTitleCase = function() {
    var newSentence = true;
    return this.split(/\s+/).map(function(word) {
        if (word == "") { return; }
        var canCapitalise = true;
        // Get the pos of the first alpha char (word might start with " or ')
        var firstAlphaCharPos = word.search(/\w/);
        // Check for uppercase char that is not the first char (might be acronym or all caps)
        if (word.search(/[A-Z]/) > 0) {
            canCapitalise = false;
        } else if (stopWordsArray.indexOf(word) != -1) {
            // Is a stop word and not a new sentence
            word.toLowerCase();
            if (!newSentence) {
                canCapitalise = false;
            }
        }
        // Is this the last word in a sentence?
        newSentence = (word.search(/[\.!\?:]['"]?$/) > 0)? true : false;
        return (canCapitalise)? word.replace(word[firstAlphaCharPos], word[firstAlphaCharPos].toUpperCase()) : word;
    }).join(' ');
}

// Pass a string using dot notation:
alert("A critical examination of Plato's view of the human nature".toTitleCase());
var str = "Ten years on: a study into the effectiveness of NCEA in New Zealand schools";
str.toTitleCase());
str = "\"Where to from here?\" the effectivness of eLearning in childhood education";
alert(str.toTitleCase());

/* Result:
A Critical Examination of Plato's View of the Human Nature.
Ten Years On: A Study Into the Effectiveness of NCEA in New Zealand Schools.
"Where to From Here?" The Effectivness of eLearning in Childhood Education. */

ES 6

str.split(' ')
   .map(s => s.slice(0, 1).toUpperCase() + s.slice(1).toLowerCase())
   .join(' ')

else

str.split(' ').map(function (s) {
    return s.slice(0, 1).toUpperCase() + s.slice(1).toLowerCase();
}).join(' ')