这是我的版本。它在每个小写英文字母后面的大写英文字母之前增加一个空格，如果需要，还会将第一个字母大写:

例如: This IsCamelCase——> This IsCamelCase 这是骆驼案——>这是骆驼案 This IsCamelCase123——>

  function camelCaseToTitleCase(camelCase){
    if (camelCase == null || camelCase == "") {
      return camelCase;
    }

    camelCase = camelCase.trim();
    var newText = "";
    for (var i = 0; i < camelCase.length; i++) {
      if (/[A-Z]/.test(camelCase[i])
          && i != 0
          && /[a-z]/.test(camelCase[i-1])) {
        newText += " ";
      }
      if (i == 0 && /[a-z]/.test(camelCase[i]))
      {
        newText += camelCase[i].toUpperCase();
      } else {
        newText += camelCase[i];
      }
    }

    return newText;
  }

基于上面的一个例子，我想出了这个:

const camelToTitle = (camelCase) => camelCase
  .replace(/([A-Z])/g, (match) => ` ${match}`)
  .replace(/^./, (match) => match.toUpperCase())
  .trim()

它适用于我，因为它使用.trim()来处理边缘情况，其中第一个字母是大写的，并且您最终有一个额外的前导空格。

参考: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/Trim

我也遇到过类似的问题，我是这样处理的:

stringValue.replace(/([A-Z]+)*([A-Z][a-z])/g, "$1 $2")

对于更健壮的解决方案:

stringValue.replace(/([A-Z]+)/g, " $1").replace(/([A-Z][a-z])/g, " $1")

http://jsfiddle.net/PeYYQ/

输入:

 helloThere 
 HelloThere 
 ILoveTheUSA
 iLoveTheUSA

输出:

 hello There 
 Hello There 
 I Love The USA
 i Love The USA

上面的答案对我来说都不完美，所以我不得不带着自己的自行车:

function camelCaseToTitle(camelCase) {
    if (!camelCase) {
        return '';
    }

    var pascalCase = camelCase.charAt(0).toUpperCase() + camelCase.substr(1);
    return pascalCase
        .replace(/([a-z])([A-Z])/g, '$1 $2')
        .replace(/([A-Z])([A-Z][a-z])/g, '$1 $2')
        .replace(/([a-z])([0-9])/gi, '$1 $2')
        .replace(/([0-9])([a-z])/gi, '$1 $2');
}

测试用例:

null => ''
'' => ''
'simpleString' => 'Simple String'
'stringWithABBREVIATIONInside => 'String With ABBREVIATION Inside'
'stringWithNumber123' => 'String With Number 123'
'complexExampleWith123ABBR890Etc' => 'Complex Example With 123 ABBR 890 Etc'

我的分裂案例解决方案的行为方式，我想:

const splitCase = s => !s || s.indexOf(' ') >= 0 ? s :
    (s.charAt(0).toUpperCase() + s.substring(1))
        .split(/(?<=[a-z])(?=[A-Z])|(?<=[A-Z])(?=[A-Z][a-z])/g)
        .map(x => x.replace(/([0-9]+)/g,'$1 '))
        .join(' ')

输入

'a,abc,TheId,TheID,TheIDWord,TheID2Word,Leave me Alone!'
.split(',').map(splitCase)
.forEach(x => console.log(x))

输出

A
Abc
The Id
The ID
The ID Word
The ID2 Word
Leave me Alone!

由于上述函数需要在JS中使用Lookbehind，而目前Safari中还没有实现，因此我重写了实现，以不使用下面的RegEx:

const isUpper = c => c >= 'A' && c <= 'Z'
const isDigit = c => c >= '0' && c <= '9'
const upperOrDigit = c => isUpper(c) || isDigit(c)

function splitCase(s) {
    let to = []
    if (typeof s != 'string') return to
    let lastSplit = 0
    for (let i=0; i<s.length; i++) {
        let c = s[i]
        let prev = i>0 ? s[i-1] : null
        let next = i+1 < s.length ? s[i+1] : null
        if (upperOrDigit(c) && (!upperOrDigit(prev) || !upperOrDigit(next))) {
            to.push(s.substring(lastSplit, i))
            lastSplit = i
        }
    }
    to.push(s.substring(lastSplit, s.length))
    return to.filter(x => !!x)
}

没有副作用的例子。

function camel2title(camelCase) {
  // no side-effects
  return camelCase
    // inject space before the upper case letters
    .replace(/([A-Z])/g, function(match) {
       return " " + match;
    })
    // replace first char with upper case
    .replace(/^./, function(match) {
      return match.toUpperCase();
    });
}

在ES6

const camel2title = (camelCase) => camelCase
  .replace(/([A-Z])/g, (match) => ` ${match}`)
  .replace(/^./, (match) => match.toUpperCase())
  .trim();