下面有一个函数称为ucfirst((缩写为“上例第一字母”):

function ucfirst(str) {
    var firstLetter = str.substr(0, 1);
    return firstLetter.toUpperCase() + str.substr(1);
}

您可以通过称 ucfirst(“某些链条”)来资本化一个链条 - 例如,

ucfirst("this is a test") --> "This is a test"

在第一行中,它提取第一Letter,然后在第二行中,它通过呼叫第一Letter.toUpperCase()来资本化第一Letter,并将其与其余的行列相结合,这是通过呼叫str.substr(1)来找到的。

你可能认为这会失败一个空的线条,而且实际上在一个语言如C,你会不得不为此加密,但是在JavaScript中,当你采取一个空的线条,你只是得到一个空的线条。

var str = "test string";
str = str.substring(0,1).toUpperCase() + str.substring(1);

String.prototype.capitalize = function(allWords) {
   return (allWords) ? // If all words
      this.split(' ').map(word => word.capitalize()).join(' ') : // Break down the phrase to words and then recursive
                                                                 // calls until capitalizing all words
      this.charAt(0).toUpperCase() + this.slice(1); // If allWords is undefined, capitalize only the first word,
                                                    // meaning the first character of the whole string
}

然后:

 "capitalize just the first word".capitalize(); ==> "Capitalize just the first word"
 "capitalize all words".capitalize(true); ==> "Capitalize All Words"

更新2016年11月(ES6),只是为了乐趣:

const capitalize = (string = '') => [...string].map(    // Convert to array with each item is a char of
                                                        // string by using spread operator (...)
    (char, index) => index ? char : char.toUpperCase()  // Index true means not equal 0, so (!index) is
                                                        // the first character which is capitalized by
                                                        // the `toUpperCase()` method
 ).join('')                                             // Return back to string

此分類上一篇: 你好(Hello)

适用于所有 Unicode 字符的解决方案

57 81 不同答案这个问题,一些离主题,但其中没有一个提出重要问题,没有一个列出的解决方案将与亚洲字符, emoji,和其他高 Unicode 点值字符在许多浏览器工作。

const consistantCapitalizeFirstLetter = "\uD852\uDF62".length === 1 ?
    function(S) {
        "use-strict"; // Hooray! The browser uses UTF-32!
        return S.charAt(0).toUpperCase() + S.substring(1);
    } : function(S) {
        "use-strict";
        // The browser is using UCS16 to store UTF-16
        var code = S.charCodeAt(0)|0;
        return (
          code >= 0xD800 && code <= 0xDBFF ? // Detect surrogate pair
            S.slice(0,2).toUpperCase() + S.substring(2) :
            S.charAt(0).toUpperCase() + S.substring(1)
        );
    };
const prettyCapitalizeFirstLetter = "\uD852\uDF62".length === 1 ?
    function(S) {
        "use-strict"; // Hooray! The browser uses UTF-32!
        return S.charAt(0).toLocaleUpperCase() + S.substring(1);
    } : function(S) {
        "use-strict";
        // The browser is using UCS16 to store UTF-16
        var code = S.charCodeAt(0)|0;
        return (
          code >= 0xD800 && code <= 0xDBFF ? // Detect surrogate pair
            S.slice(0,2).toLocaleUpperCase() + S.substring(2) :
            S.charAt(0).toLocaleUpperCase() + S.substring(1)
        );
    };

请注意,上述解决方案试图计算 UTF-32. 然而,规格正式表示,浏览器必须在 UTF-16 地图中完成一切。 然而,如果我们都聚集在一起,做我们的部分,并开始为 UTF32 做好准备,那么 TC39 可能会允许浏览器开始使用 UTF-32 (就像 Python 如何使用 24 位字符的每个字符一样)

function capitalize(s) {
    // returns the first letter capitalized + the string from index 1 and out aka. the rest of the string
    return s[0].toUpperCase() + s.substr(1);
}


// examples
capitalize('this is a test');
=> 'This is a test'

capitalize('the Eiffel Tower');
=> 'The Eiffel Tower'

capitalize('/index.html');
=> '/index.html'

function cap(input) {
    return input.replace(/[\.\r\n\t\:\;\?\!]\W*(\w)/g, function(match, capture) {
         // For other sentences in the text
         return match.toUpperCase();
    }).replace(/^\W*\w/, function(match, capture) {
        // For the first sentence in the text
        return match.toUpperCase();
    });;
}

var a = "hi, dear user. it is a simple test. see you later!\r\nbye";
console.log(cap(a));
// Output: Hi, dear user. It is a simple test. See you later!
// Bye