这里我使用了replace()函数。

function titleCase(str){
    return str.replace(/\w\S*/g, function(txt){return txt.charAt(0).toUpperCase() + txt.substr(1).toLowerCase();});
}

/* 1. Transform your string into lower case
   2. Split your string into an array. Notice the white space I'm using for the separator
   3. Iterate the new array, and assign the current iteration value (array[c]) a new formatted string:
      - With the sentence: array[c][0].toUpperCase() the first letter of the string converts to upper case.
      - With the sentence: array[c].substring(1) we get the rest of the string (from the second letter index to the last one).
      - The "add" (+) character is for concatenate both strings.
   4. return array.join(' ') // Returns the formatted array like a new string. */


function titleCase(str){
    str = str.toLowerCase();
    var array = str.split(' ');
    for(var c = 0; c < array.length; c++){
        array[c] = array[c][0].toUpperCase() + array[c].substring(1);
    }
    return array.join(' ');
}

titleCase("I'm a little tea pot");

这里我使用了三个函数toLowerCase()， toUpperCase()和replace(regex,replacer)

function titleCase(str) { 
     return str.toLowerCase().replace(/^(\w)|\s(\w)/g, (grp) => grp.toUpperCase()); 
}

titleCase(“我是一个小茶壶”);

用奇数分隔符将字符串中的每个单词大写(不使用正则表达式的快速解决方案)

function capitalizeFirstLetter(str) {
  function isLetter(char) {
    const code = char.charCodeAt(0);
    // Considering apostrophe (char code 39) as a letter
    return code > 64 && code < 91 || code > 96 && code < 123 || char.charCodeAt(0) === 39;
  }

  str = str.toLowerCase();

  let newStr = '';
  let processingWord = false;

  for (let i = 0; i < str.length; i += 1) {
    if (!processingWord && isLetter(str[i])) {
      processingWord = true;
      newStr += str[i].toUpperCase();
    }
    else {
      newStr += str[i];
    }

    if (processingWord && !isLetter(str[i])) {
      processingWord = false;
    }
  }

  return newStr;
}

// stack overflow -> Stack Overflow
// ping-pong -> Ping-Pong
// domino's pizza -> Domino's Pizza
// /some/path -> /Some/Path

这里有一个简单的一行代码

const ucFirst = t => t.replace(/(^|\s)[A-Za-zÀ-ÖØ-öø-ÿ]/g, c => c.toUpperCase());

注意，它只改变每个单词的首字母大小写，你可能想这样使用它:

console.log(ucFirst('foO bAr'));
// FoO BAr

console.log(ucFirst('foO bAr'.toLowerCase()));
// Foo Bar

// works with accents too
console.log(ucFirst('éfoO bAr'));
// ÉfoO BAr

或者基于String。这里的原型是一个处理几种模式:

String.prototype.ucFirst = function (mode = 'eachWord') {
  const modes = {
    eachWord: /(^|\s)[A-Za-zÀ-ÖØ-öø-ÿ]/g,
    firstWord: /(^|\s)[A-Za-zÀ-ÖØ-öø-ÿ]/,
    firstChar: /^[A-Za-zÀ-ÖØ-öø-ÿ]/,
    firstLetter: /[A-Za-zÀ-ÖØ-öø-ÿ]/,
  };

  if (mode in modes) {
    return this.replace(modes[mode], c => c.toUpperCase());
  } else {
    throw `error: ucFirst invalid mode (${mode}). Parameter should be one of: ` + Object.keys(modes).join('|');
  }
};

console.log('eachWord', 'foO bAr'.ucFirst());
// FoO BAr

console.log('eachWord', 'foO bAr'.toLowerCase().ucFirst());
// Foo Bar

console.log('firstWord', '1foO bAr'.ucFirst('firstWord'));
// 1foO BAr

console.log('firstChar', '1foO bAr'.ucFirst('firstChar'));
// 1foO bAr

console.log('firstLetter', '1foO bAr'.ucFirst('firstLetter'));
// 1FoO bAr

编辑:

或者基于String。处理多种模式和可选的第二个参数来指定单词分隔符(String或RegExp)的原型:

String.prototype.ucFirst = function (mode = 'eachWord', wordSeparator = /\s/) {
  const letters = /[A-Za-zÀ-ÖØ-öø-ÿ]/;
  const ws =
    '^|' +
    (wordSeparator instanceof RegExp
      ? '(' + wordSeparator.source + ')'
      : // sanitize string for RegExp https://stackoverflow.com/questions/3446170/escape-string-for-use-in-javascript-regex#comment52837041_6969486
        '[' + wordSeparator.replace(/[[{}()*+?^$|\]\.\\]/g, '\\$&') + ']');

  const r =
    mode === 'firstLetter'
      ? letters
      : mode === 'firstChar'
      ? new RegExp('^' + letters.source)
      : mode === 'firstWord' || mode === 'eachWord'
      ? new RegExp(
          '(' + ws + ')' + letters.source,
          mode === 'eachWord' ? 'g' : undefined
        )
      : undefined;

  if (r) {
    return this.replace(r, (c) => c.toUpperCase());
  } else {
    throw `error: ucFirst invalid mode (${mode}). Parameter should be one of: firstLetter|firstChar|firstWord|eachWord`;
  }
};

console.log("mike o'hara".ucFirst('eachWord', " \t\r\n\f\v'"));
// Mike O'Hara
console.log("mike o'hara".ucFirst('eachWord', /[\s']/));
// Mike O'Hara

ECMA2017或ES8

const titleCase = (string) => { return string .split(' ') .map(word => word.substr(0,1).toUpperCase() + word.substr(1,word.length)) .join(' '); }; let result = titleCase('test test test'); console.log(result); Explanation: 1. First, we pass the string "test test test" to our function "titleCase". 2. We split a string on the space basis so the result of first function "split" will be ["test","test","test"] 3. As we got an array, we used map function for manipulation each word in the array. We capitalize the first character and add remaining character to it. 4. In the last, we join the array using space as we split the string by sapce.