瓦尔·弦=“测试” 笨蛋。 var输出=弦。charAt(0) 控制台日志(输出)。 警报(输出)

  
 var string = "tEsT"

 string = string.toLowerCase() 

 string.charAt(0).toUpperCase() + string.slice(1)

string.charAt(0) returns the character at the 0th index of the string. toUpperCase() is a method that returns the uppercase equivalent of a string. It is applied to the first character of the string, returned by charAt(0). string.slice(1) returns a new string that starts from the 1st index (the character at index 0 is excluded) till the end of the string. Finally, the expression concatenates the result of toUpperCase() and string.slice(1) to create a new string with the first character capitalized.

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。

试试这个，最短的方法:

str.replace(/(^[a-z])|(\s+[a-z])/g, txt => txt.toUpperCase());

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();
  });
}

只是另一个版本的混合。这也将检查字符串是否。长度为0:

String.prototype.toTitleCase = function() {
    var str = this;
    if(!str.length) {
        return "";
    }
    str = str.split(" ");
    for(var i = 0; i < str.length; i++) {
        str[i] = str[i].charAt(0).toUpperCase() + (str[i].substr(1).length ? str[i].substr(1) : '');
    }
    return (str.length ? str.join(" ") : str);
};

"john f. kennedy".replace(/\b\S/g, t => t.toUpperCase())