String.prototype.capitalize = function() {
    return this.toLowerCase().split(' ').map(capFirst).join(' ');
    function capFirst(str) {
        return str.length === 0 ? str : str[0].toUpperCase() + str.substr(1);
    }
}

用法:

"hello world".capitalize()

下面是我的函数，它转换为标题大小写，但也保留了定义的首字母缩写为大写，小词为小写:

String.prototype.toTitleCase = function() {
  var i, j, str, lowers, uppers;
  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
  lowers = ['A', 'An', 'The', 'And', 'But', 'Or', 'For', 'Nor', 'As', 'At', 
  'By', 'For', 'From', 'In', 'Into', 'Near', 'Of', 'On', 'Onto', 'To', 'With'];
  for (i = 0, j = lowers.length; i < j; 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
  uppers = ['Id', 'Tv'];
  for (i = 0, j = uppers.length; i < j; i++)
    str = str.replace(new RegExp('\\b' + uppers[i] + '\\b', 'g'), 
      uppers[i].toUpperCase());

  return str;
}

例如:

"TO LOGIN TO THIS SITE and watch tv, please enter a valid id:".toTitleCase();
// Returns: "To Login to This Site and Watch TV, Please Enter a Valid ID:"

大多数答案似乎忽略了使用单词边界元字符(\b)的可能性。Greg Dean使用它的回答的简短版本:

function toTitleCase(str)
{
    return str.replace(/\b\w/g, function (txt) { return txt.toUpperCase(); });
}

也适用于连字符的名字，如吉姆-鲍勃。

约翰·史密斯->约翰·史密斯

'john smith'.replace(/(^\w|\s+\w){1}/g, function(str){ return str.toUpperCase() } );

如果你需要一个语法正确的答案:

这个答案考虑了介词，如“of”，“from”，… 输出将生成您希望在论文中看到的编辑风格的标题。

toTitleCase函数

考虑此处列出的语法规则的函数。 该函数还合并空格和删除特殊字符(根据需要修改regex)

const toTitleCase = (str) => {
  const articles = ['a', 'an', 'the'];
  const conjunctions = ['for', 'and', 'nor', 'but', 'or', 'yet', 'so'];
  const prepositions = [
    'with', 'at', 'from', 'into','upon', 'of', 'to', 'in', 'for',
    'on', 'by', 'like', 'over', 'plus', 'but', 'up', 'down', 'off', 'near'
  ];

  // The list of spacial characters can be tweaked here
  const replaceCharsWithSpace = (str) => str.replace(/[^0-9a-z&/\\]/gi, ' ').replace(/(\s\s+)/gi, ' ');
  const capitalizeFirstLetter = (str) => str.charAt(0).toUpperCase() + str.substr(1);
  const normalizeStr = (str) => str.toLowerCase().trim();
  const shouldCapitalize = (word, fullWordList, posWithinStr) => {
    if ((posWithinStr == 0) || (posWithinStr == fullWordList.length - 1)) {
      return true;
    }

    return !(articles.includes(word) || conjunctions.includes(word) || prepositions.includes(word));
  }

  str = replaceCharsWithSpace(str);
  str = normalizeStr(str);

  let words = str.split(' ');
  if (words.length <= 2) { // Strings less than 3 words long should always have first words capitalized
    words = words.map(w => capitalizeFirstLetter(w));
  }
  else {
    for (let i = 0; i < words.length; i++) {
      words[i] = (shouldCapitalize(words[i], words, i) ? capitalizeFirstLetter(words[i], words, i) : words[i]);
    }
  }

  return words.join(' ');
}

确保正确性的单元测试

import { expect } from 'chai';
import { toTitleCase } from '../../src/lib/stringHelper';

describe('toTitleCase', () => {
  it('Capitalizes first letter of each word irrespective of articles, conjunctions or prepositions if string is no greater than two words long', function(){
    expect(toTitleCase('the dog')).to.equal('The Dog'); // Capitalize articles when only two words long
    expect(toTitleCase('for all')).to.equal('For All'); // Capitalize conjunctions when only two words long
    expect(toTitleCase('with cats')).to.equal('With Cats'); // Capitalize prepositions when only two words long
  });

  it('Always capitalize first and last words in a string irrespective of articles, conjunctions or prepositions', function(){
    expect(toTitleCase('the beautiful dog')).to.equal('The Beautiful Dog');
    expect(toTitleCase('for all the deadly ninjas, be it so')).to.equal('For All the Deadly Ninjas Be It So');
    expect(toTitleCase('with cats and dogs we are near')).to.equal('With Cats and Dogs We Are Near');
  });

  it('Replace special characters with space', function(){
    expect(toTitleCase('[wolves & lions]: be careful')).to.equal('Wolves & Lions Be Careful');
    expect(toTitleCase('wolves & lions, be careful')).to.equal('Wolves & Lions Be Careful');
  });

  it('Trim whitespace at beginning and end', function(){
    expect(toTitleCase(' mario & Luigi superstar saga ')).to.equal('Mario & Luigi Superstar Saga');
  });

  it('articles, conjunctions and prepositions should not be capitalized in strings of 3+ words', function(){
    expect(toTitleCase('The wolf and the lion: a tale of two like animals')).to.equal('The Wolf and the Lion a Tale of Two like Animals');
    expect(toTitleCase('the  three Musketeers  And plus ')).to.equal('The Three Musketeers and Plus');
  });
});

请注意，我从提供的字符串中删除了相当多的特殊字符。您将需要调整正则表达式以满足项目的需求。

我做了这个函数，它可以处理姓氏(所以它不是标题大小写)，如“McDonald”或“MacDonald”或“O'Toole”或“D'Orazio”。然而，它不能处理带有“van”或“von”的德语或荷兰语名称，这些名称通常是小写的。我相信“de”也经常是小写的，比如“Robert de Niro”。这些问题仍需解决。

function toProperCase(s)
{
  return s.toLowerCase().replace( /\b((m)(a?c))?(\w)/g,
          function($1, $2, $3, $4, $5) { if($2){return $3.toUpperCase()+$4+$5.toUpperCase();} return $1.toUpperCase(); });
}