Capitalize First Letter Of Each Word In A String - JavaScript

问题

What is wrong with this function? I am lost thanks for help.

function titleCase(str) {
 var splitStr = str.toLowerCase().split(\' \');
 for (var i = 0; i < splitStr.length; i++) {
   if (splitStr.length[i] < splitStr.length) {
     splitStr[i].charAt(0).toUpperCase();     
   }
      str = splitStr.join(\' \'); 
 }
return str;
}

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

回答1:

You are not assigning your changes to the array again, so all your efforts are in vain. Try this:

function titleCase(str) {
   var splitStr = str.toLowerCase().split(' ');
   for (var i = 0; i < splitStr.length; i++) {
       // You do not need to check if i is larger than splitStr length, as your for does that for you
       // Assign it back to the array
       splitStr[i] = splitStr[i].charAt(0).toUpperCase() + splitStr[i].substring(1);     
   }
   // Directly return the joined string
   return splitStr.join(' '); 
}

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

回答2:

You are making complex a very easy thing. You can add this in your CSS:

 .capitalize {
    text-transform: capitalize;   
  }

In javascript, you can add the class to an element

 document.getElementById("element").className="capitalize";

回答3:

ES6 version:

const toTitleCase = (phrase) => {
  return phrase
    .toLowerCase()
    .split(' ')
    .map(word => word.charAt(0).toUpperCase() + word.slice(1))
    .join(' ');
};

let result = toTitleCase('maRy hAd a lIttLe LaMb');
console.log(result);

回答4:

If you can use thirdparty library then lodash has a helper function for you.

https://lodash.com/docs/4.17.3#startCase

_.startCase('foo bar');
// => 'Foo Bar'

_.startCase('--foo-bar--');
// => 'Foo Bar'
 
_.startCase('fooBar');
// => 'Foo Bar'
 
_.startCase('__FOO_BAR__');
// => 'FOO BAR'

<script src="https://cdn.jsdelivr.net/lodash/4.17.3/lodash.min.js"></script>

回答5:

in ES6 one line answer using arrow function

const captialize = words => words.split(' ').map( w =>  w.substring(0,1).toUpperCase()+ w.substring(1)).join(' ')

回答6:

𝗙𝗮𝘀𝘁𝗲𝘀𝘁 𝗦𝗼𝗹𝘂𝘁𝗶𝗼𝗻 𝗙𝗼𝗿 𝗟𝗮𝘁𝗶𝗻-𝗜 𝗖𝗵𝗮𝗿𝗮𝗰𝘁𝗲𝗿𝘀

You could simply use a regular expression function to change the capitalization of each letter. With V8 JIST optimizations, this should prove to be the fast and memory efficient.

// Only works on Latin-I strings
'tHe VeRy LOOong StRINg'.replace(/\b[a-z]|['_][a-z]|\B[A-Z]/g, function(x){return x[0]==="'"||x[0]==="_"?x:String.fromCharCode(x.charCodeAt(0)^32)})

Or, as a function:

// Only works for Latin-I strings
var fromCharCode = String.fromCharCode;
var firstLetterOfWordRegExp = /\b[a-z]|['_][a-z]|\B[A-Z]/g;
function toLatin1UpperCase(x){ // avoid frequent anonymous inline functions
    var charCode = x.charCodeAt(0);
    return charCode===39 ? x : fromCharCode(charCode^32);
}
function titleCase(string){
    return string.replace(firstLetterOfWordRegExp, toLatin1UpperCase);
}

According to this benchmark, the code is over 33% faster than the next best solution in Chrome.

𝗗𝗲𝗺𝗼

<textarea id="input" type="text">I'm a little tea pot</textarea><br /><br />
<textarea id="output" type="text" readonly=""></textarea>
<script>
(function(){
    "use strict"
    var fromCode = String.fromCharCode;
    function upper(x){return x[0]==="'"?x:fromCode(x.charCodeAt(0) ^ 32)}
    (input.oninput = function(){
      output.value = input.value.replace(/\b[a-z]|['_][a-z]|\B[A-Z]/g, upper);
    })();
})();
</script>

回答7:

ES2015 version:

const titleCase = title => title
    .split(/ /g).map(word => 
        `${word.substring(0,1).toUpperCase()}${word.substring(1)}`)
    .join("");

回答8:

Also a good option (particularly if you're using freeCodeCamp):

function titleCase(str) {
  var wordsArray = str.toLowerCase().split(/\s+/);
  var upperCased = wordsArray.map(function(word) {
    return word.charAt(0).toUpperCase() + word.substr(1);
  });
  return upperCased.join(" ");
}

回答9:

I usually prefer not to use regexp because of readability and also I try to stay away from loops. I think this is kind of readable.

function capitalizeFirstLetter(string) {
    return string && string.charAt(0).toUpperCase() + string.substring(1);
};

回答10:

This routine will handle hyphenated words and words with apostrophe.

function titleCase(txt) {
var firstLtr = 0;
for (var i = 0;i < text.length;i++){
    if (i == 0 &&/[a-zA-Z]/.test(text.charAt(i))) firstLtr = 2;
    if (firstLtr == 0 &&/[a-zA-Z]/.test(text.charAt(i))) firstLtr = 2;
    if (firstLtr == 1 &&/[^a-zA-Z]/.test(text.charAt(i))){
        if (text.charAt(i) == "'"){
            if (i + 2 == text.length &&/[a-zA-Z]/.test(text.charAt(i + 1))) firstLtr = 3;
            else if (i + 2 < text.length &&/[^a-zA-Z]/.test(text.charAt(i + 2))) firstLtr = 3;
        }
    if (firstLtr == 3) firstLtr = 1;
    else firstLtr = 0;
    }
    if (firstLtr == 2){
        firstLtr = 1;
        text = text.substr(0, i) + text.charAt(i).toUpperCase() + text.substr(i + 1);
    }
    else {
        text = text.substr(0, i) + text.charAt(i).toLowerCase() + text.substr(i + 1);
    }
}

}

titleCase("pAt o'Neil's"); // returns "Pat O'Neil's";

回答11:

function titleCase(str) {

var myString = str.toLowerCase().split(' ');
for (var i = 0; i < myString.length; i++) {
    var subString = myString[i].split('');
    for (var j = 0; j < subString.length; j++) {
        subString[0] = subString[0].toUpperCase();

    }
    myString[i] = subString.join('');
}

return myString.join(' '); }

回答12:

Or can be done using replace(), and replace each word's first letter with its "upperCase".

function titleCase(str) {
  return str.toLowerCase().split(' ').map(function(word) {
     return word.replace(word[0], word[0].toUpperCase());
      }).join(' ');
}

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

回答13:

text-transform: capitalize;

Css has got it :)

回答14:

function LetterCapitalize(str) { 
  return str.split(" ").map(item=>item.substring(0,1).toUpperCase()+item.substring(1)).join(" ")
}

回答15:

The function below does not change any other part of the string than trying to convert all the first letters of all words (i.e. by the regex definition \w+) to uppercase.

That means it does not necessarily convert words to Titlecase, but does exactly what the title of the question says: "Capitalize First Letter Of Each Word In A String - JavaScript"

• Don't split the string
• determine each word by the regex \w+ that is equivalent to [A-Za-z0-9_]+
  • apply function String.prototype.toUpperCase() only to the first character of each word.

function first_char_to_uppercase(argument) {
  return argument.replace(/\w+/g, function(word) {
    return word.charAt(0).toUpperCase() + word.slice(1);
  });
}

Examples:

first_char_to_uppercase("I'm a little tea pot");
// "I'M A Little Tea Pot"
// This may look wrong to you, but was the intended result for me
// You may wanna extend the regex to get the result you desire, e.g., /[\w']+/

first_char_to_uppercase("maRy hAd a lIttLe LaMb");
// "MaRy HAd A LIttLe LaMb"
// Again, it does not convert words to Titlecase

first_char_to_uppercase(
  "ExampleX: CamelCase/UPPERCASE&lowercase,exampleY:N0=apples"
);
// "ExampleX: CamelCase/UPPERCASE&Lowercase,ExampleY:N0=Apples"

first_char_to_uppercase("…n1=orangesFromSPAIN&&n2!='a sub-string inside'");
// "…N1=OrangesFromSPAIN&&N2!='A Sub-String Inside'"

first_char_to_uppercase("snake_case_example_.Train-case-example…");
// "Snake_case_example_.Train-Case-Example…"
// Note that underscore _ is part of the RegEx \w+

first_char_to_uppercase(
  "Capitalize First Letter of each word in a String - JavaScript"
);
// "Capitalize First Letter Of Each Word In A String - JavaScript"

Edit 2019-02-07: If you want actual Titlecase (i.e. only the first letter uppercase all others lowercase):

function titlecase_all_words(argument) {
  return argument.replace(/\w+/g, function(word) {
    return word.charAt(0).toUpperCase() + word.slice(1).toLowerCase();
  });
}

Examples showing both:

test_phrases = [
  "I'm a little tea pot",
  "maRy hAd a lIttLe LaMb",
  "ExampleX: CamelCase/UPPERCASE&lowercase,exampleY:N0=apples",
  "…n1=orangesFromSPAIN&&n2!='a sub-string inside'",
  "snake_case_example_.Train-case-example…",
  "Capitalize First Letter of each word in a String - JavaScript"
];
for (el in test_phrases) {
  let phrase = test_phrases[el];
  console.log(
    phrase,
    "<- input phrase\n",
    first_char_to_uppercase(phrase),
    "<- first_char_to_uppercase\n",
    titlecase_all_words(phrase),
    "<- titlecase_all_words\n "
  );
}

// I'm a little tea pot <- input phrase
// I'M A Little Tea Pot <- first_char_to_uppercase
// I'M A Little Tea Pot <- titlecase_all_words

// maRy hAd a lIttLe LaMb <- input phrase
// MaRy HAd A LIttLe LaMb <- first_char_to_uppercase
// Mary Had A Little Lamb <- titlecase_all_words

// ExampleX: CamelCase/UPPERCASE&lowercase,exampleY:N0=apples <- input phrase
// ExampleX: CamelCase/UPPERCASE&Lowercase,ExampleY:N0=Apples <- first_char_to_uppercase
// Examplex: Camelcase/Uppercase&Lowercase,Exampley:N0=Apples <- titlecase_all_words

// …n1=orangesFromSPAIN&&n2!='a sub-string inside' <- input phrase
// …N1=OrangesFromSPAIN&&N2!='A Sub-String Inside' <- first_char_to_uppercase
// …N1=Orangesfromspain&&N2!='A Sub-String Inside' <- titlecase_all_words

// snake_case_example_.Train-case-example… <- input phrase
// Snake_case_example_.Train-Case-Example… <- first_char_to_uppercase
// Snake_case_example_.Train-Case-Example… <- titlecase_all_words

// Capitalize First Letter of each word in a String - JavaScript <- input phrase
// Capitalize First Letter Of Each Word In A String - JavaScript <- first_char_to_uppercase
// Capitalize First Letter Of Each Word In A String - Javascript <- titlecase_all_words

回答16:

Below is another way to capitalize first alphabet of each word in a string.

Create a custom method for String object by using prototype.

  String.prototype.capitalize = function() {
      var c = '';
      var s = this.split(' ');
      for (var i = 0; i < s.length; i++) {
          c+= s[i].charAt(0).toUpperCase() + s[i].slice(1) + ' ';
      }
      return c;
  }
  var name = "john doe";
  document.write(name.capitalize());

回答17:

I think this way should be faster; cause it doesn't split string and join it again; just using regex.

var str = text.replace(/(^\w{1})|(\s{1}\w{1})/g, match => match.toUpperCase());

Explanation:

1. (^\w{1}): match first char of string
2. |: or
3. (\s{1}\w{1}): match one char that came after one space
4. g: match all
5. match => match.toUpperCase(): replace with can take function, so; replace match with upper case match

回答18:

Raw code:

function capi(str) {
    var s2 = str.trim().toLowerCase().split(' ');
  var s3 = [];
  s2.forEach(function(elem, i) {
          s3.push(elem.charAt(0).toUpperCase().concat(elem.substring(1)));  
  });
  return s3.join(' ');
}
capi('js string exasd');

回答19:

Used replace() with RegExp

function titleCase(str) {

  var newStr = str.toLowerCase().replace(/./, (x) => x.toUpperCase()).replace(/[^']\b\w/g, (y) => y.toUpperCase());


console.log(newStr);

}

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

回答20:

Here's how you could do it with the map function basically, it does the same as the accepted answer but without the for-loop. Hence, saves you few lines of code.

function titleCase(text) {
  if (!text) return text;
  if (typeof text !== 'string') throw "invalid argument";

  return text.toLowerCase().split(' ').map(value => {
    return value.charAt(0).toUpperCase() + value.substring(1);
  }).join(' ');
}

console.log(titleCase("I'm A little tea pot"));

回答21:

let cap = (str) => {
  let arr = str.split(' ');
  arr.forEach(function(item, index) {
    arr[index] = item.replace(item[0], item[0].toUpperCase());
  });

  return arr.join(' ');
};

console.log(cap("I'm a little tea pot"));

Fast Readable Version see benchmark http://jsben.ch/k3JVz

回答22:

/* 1. Transform your string into lower case
2. Split your string into an array. Notice the white space i'm using for 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");

回答23:

Please check the code below.

function titleCase(str) {
  var splitStr = str.toLowerCase().split(' ');
  var nstr = ""; 
  for (var i = 0; i < splitStr.length; i++) {
    nstr +=  (splitStr[i].charAt(0).toUpperCase()+ splitStr[i].slice(1) + " 
    ");
  }
  console.log(nstr);
}

var strng = "this is a new demo for checking the string";
titleCase(strng);

回答24:

A more compact (and modern) rewrite of @somethingthere's proposed solution:

function titleCase(str) {
    return str.toLowerCase().split(' ').map(function(chunk){
        return chunk.charAt(0).toUpperCase() + chunk.substring(1);
    }).join(' ');
}
    
document.write(titleCase("I'm an even smaller tea pot"));

回答25:

As of ECMA2017 or 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.

回答26:

function titleCase(str) {
  //First of all, lets make all the characters lower case
  let lowerCaseString = "";
  for (let i = 0; i < str.length; i++) {
    lowerCaseString = lowerCaseString + str[i].toLowerCase();
  }
  //Now lets make the first character in the string and the character after the empty character upper case and leave therest as it is
  let i = 0;
  let upperCaseString = "";
  while (i < lowerCaseString.length) {
    if (i == 0) {
      upperCaseString = upperCaseString + lowerCaseString[i].toUpperCase();
    } else if (lowerCaseString[i - 1] == " ") {
      upperCaseString = upperCaseString + lowerCaseString[i].toUpperCase();
    } else {
      upperCaseString = upperCaseString + lowerCaseString[i];
    }
    i = i + 1;
  }
  console.log(upperCaseString);

  return upperCaseString;
}

titleCase("hello woRLD");

来源：https://stackoverflow.com/questions/32589197/capitalize-first-letter-of-each-word-in-a-string-javascript