Convert string to sentence case in javascript

Question

I want a string entered should be converted to sentence case in whatever case it is.

Like

hi all, this is derp. thank you all to answer my query.

be converted to

Hi all, this is derp. Thank you all to answer my query.

Hint: Try writing a regular expression. Find the first letter of sentences and use periods+spaces to delimit sentences. Good luck. If you still need help after attempting the regex, post it here and we'll see what we can do. — Jackson, Sep 30 '13 at 08:20
NB: not all period characters indicate the end of a sentence. — Alnitak, Sep 30 '13 at 08:38

score 22 · Answer 1 · edited Sep 17 '15 at 20:39

22

I came up with this kind of RegExp:

var rg = /(^\w{1}|\.\s*\w{1})/gi;
var myString = "hi all, this is derp. thank you all to answer my query.";
myString = myString.replace(rg, function(toReplace) {
    return toReplace.toUpperCase();
});

edited Sep 17 '15 at 20:39

answered Sep 30 '13 at 08:29

Samuli Hakoniemi

18,740
1
61
74

Ok, I'll add that one asterisk in there and it will. – Samuli Hakoniemi Sep 30 '13 at 11:00
but it will not work for space in starting of " hi all,----" .you have to edit that too. – unknownbits Sep 30 '13 at 11:38
1

var rg = /(^\s*\w{1}|\.\s*\w{1})/gi; It will work . please update. – unknownbits Sep 30 '13 at 11:54
2

I answered to the question that was originally posted. If OP wants to make specific changes to all possible cases (including typos etc.), he has to learn regular expressions himself. This answer was shortest availabe + it's demonstrating using variables inside regexps and looping them through in replace() function. – Samuli Hakoniemi Sep 30 '13 at 12:13

score 7 · Accepted Answer · edited Sep 17 '15 at 20:00

7

Try this, It will work fine for you. It will also work for String having leading spaces.

var string="hi all, this is derp. thank you all to answer my query.";
var n=string.split(".");
var vfinal=""
for(i=0;i<n.length;i++)
{
   var spaceput=""
   var spaceCount=n[i].replace(/^(\s*).*$/,"$1").length;
   n[i]=n[i].replace(/^\s+/,"");
   var newstring=n[i].charAt(n[i]).toUpperCase() + n[i].slice(1);
   for(j=0;j<spaceCount;j++)
   spaceput=spaceput+" ";
   vfinal=vfinal+spaceput+newstring+".";
 }
 vfinal=vfinal.substring(0, vfinal.length - 1);
 alert(vfinal);

edited Sep 17 '15 at 20:00

answered Sep 30 '13 at 10:33

prytsh

84
6

great. this will work for leading space in a string. – unknownbits Sep 30 '13 at 10:39
awesome answer. Helps a lot – Ratna Srikanth Apr 30 '15 at 10:04

score 2 · Answer 3 · edited Jun 20 '20 at 09:12

Here's my modification of this post which was for changing to Title Case.

You could immediately toLowerCase the string, and then just toUpperCase the first letter of each word. Becomes a very simple 1 liner:

Instead of making it every word. This example is compatible with multiple lines and strings like A.M. and P.M. and of course, any word proceeding a period and a whitespace character.

You could add your own custom words below that toLowerCaseNames function and toUpperCaseNames in that example below.

// Based off this post: https://stackoverflow.com/a/40111894/8262102
var str = '-------------------\nhello world!\n\n2 Line Breaks. What is going on with this string. L.M.A.O.\n\nThee End...\nlower case example 1\nlower case example 2\n-------------------\nwait there\'s more!\n-------------------\nhi all, this is derp. thank you all to answer my query.';
function toTitleCase(str) {
 return str.toLowerCase().replace(/\.\s*([a-z])|^[a-z]/gm, s => s.toUpperCase());
}

// Add your own names here to override to lower case
function toLowerCaseNames(str) {
  return str.replace(/\b(lower case example 1|lower case example 2)\b/gmi, s => s.toLowerCase());
}

// Add your own names here to override to UPPER CASE
function toUpperCaseNames(str) {
  return str.replace(/\b(hello|string)\b/gmi, s => s.toUpperCase());
}

console.log(toLowerCaseNames(toUpperCaseNames(toTitleCase(str))));

You can paste all those regexp above into https://regexr.com/ to break down how they work.

score 1 · Answer 4 · edited Apr 07 '16 at 19:39

Try Demo

http://jsfiddle.net/devmgs/6hrv2/

function sentenceCase(strval){

 var newstrs = strval.split(".");
    var finalstr="";
    //alert(strval);
    for(var i=0;i<newstrs.length;i++)
        finalstr=finalstr+"."+ newstrs[i].substr(0,2).toUpperCase()+newstrs[i].substr(2);
    return finalstr.substr(1);
}

Beware all dot doesn't always represent end of line and may be abbreviations etc. Also its not sure if one types a space after the full stop. These conditions make this script vulnerable.

score 1 · Answer 5 · answered Apr 17 '20 at 16:34

The following SentenceCase code works fine for me and also handles abbreviations such e.g. a.m. and so on. May require improvements.

//=============================
// SentenceCase Function
// Copes with abbreviations
// Mohsen Alyafei (12-05-2017)
//=============================

function stringSentenceCase(str) {
  return str.replace(/\.\s+([a-z])[^\.]|^(\s*[a-z])[^\.]/g, s => s.replace(/([a-z])/,s => s.toUpperCase()))
}
//=============================

console.log(stringSentenceCase(" start sentence.   second sentence . e.g. a.m. p.m."))
console.log(stringSentenceCase("first sentence. second sentence."))
console.log(stringSentenceCase("e.g. a.m. p.m. P.M. another sentence"))

score 0 · Answer 6 · edited Sep 30 '13 at 10:56

You can also try this

<script>
var name="hi all, this is derp. thank you all to answer my query.";
var n = name.split(".");
var newname="";
for(var i=0;i<n.length;i++)
{
var j=0;
while(j<n[i].length)
{
if(n[i].charAt(j)!= " ")
    {
        n[i] = n[i].replace(n[i].charAt(j),n[i].charAt(j).toUpperCase());
            break;
    }
else
  j++;
}

newname = newname.concat(n[i]+".");
 }
alert(newname);
 </script>

score 0 · Answer 7 · answered Nov 26 '13 at 16:07

This is the solution I ended up using:

str = 'hi all, this is derp. thank you all to answer my query.';
temp_arr = str.split('.');
for (i = 0; i < temp_arr.length; i++) {
temp_arr[i]=temp_arr[i].trim()
temp_arr[i] = temp_arr[i].charAt(0).toUpperCase() + temp_arr[i].substr(1).toLowerCase();
}
str=temp_arr.join('. ') + '.';
return str;

score 0 · Answer 8 · answered Dec 06 '15 at 12:23

The below code is working for me as expected.

   function toSentenceCase(inputString) {
        inputString = "." + inputString;
   var result = "";
   if (inputString.length == 0) {
       return result;
   }

   var terminalCharacterEncountered = false;
   var terminalCharacters = [".", "?", "!"];
   for (var i = 0; i < inputString.length; i++) {
       var currentChar = inputString.charAt(i);
       if (terminalCharacterEncountered) {
           if (currentChar == ' ') {
               result = result + currentChar;
           } else {
               var currentCharToUpperCase = currentChar.toUpperCase();
               result = result + currentCharToUpperCase;
               terminalCharacterEncountered = false;
           }
       } else {
           var currentCharToLowerCase = currentChar.toLowerCase();
           result = result + currentCharToLowerCase;
       }
       for (var j = 0; j < terminalCharacters.length; j++) {
           if (currentChar == terminalCharacters[j]) {
               terminalCharacterEncountered = true;
               break;
           }
       }
   }
        result = result.substring(1, result.length - 1);
   return result;
 }

score 0 · Answer 9 · answered Sep 13 '16 at 23:03

I wrote an FSM-based function to coalesce multiple whitespace characters and convert a string to sentence-case. It should be fast because it doesn't use complex regular-expression or split and assuming your JavaScript runtime has efficient string concatenation then this should be the fastest way to do it. It also lets you easily add special-case exceptions.

Performance can probably be improved further by replacing the whitespace regexs with a function to compare char-codes.

function toSentenceCase(str) {

    var states = {
        EndOfSentence  : 0,
        EndOfSentenceWS: 1, // in whitespace immediately after end-of-sentence
        Whitespace     : 2,
        Word           : 3
    };

    var state = states.EndOfSentence;
    var start = 0;
    var end   = 0;

    var output = "";
    var word = "";

    function specialCaseWords(word) {
        if( word == "i" ) return "I";
        if( word == "assy" ) return "assembly";
        if( word == "Assy" ) return "Assembly";
        return word;
    }

    for(var i = 0; i < str.length; i++) {

        var c = str.charAt(i);

        switch( state ) {
            case states.EndOfSentence:

                if( /\s/.test( c ) ) { // if char is whitespace

                    output += " "; // append a single space character
                    state = states.EndOfSentenceWS;
                }
                else {
                    word += c.toLocaleUpperCase();
                    state = states.Word;
                }

                break;

            case states.EndOfSentenceWS:

                if( !( /\s/.test( c ) ) ) { // if char is NOT whitespace

                    word += c.toLocaleUpperCase();
                    state = states.Word;
                }

                break;
            case states.Whitespace:

                if( !( /\s/.test( c ) ) ) { // if char is NOT whitespace

                    output += " "; // add a single whitespace character at the end of the current whitespace region only if there is non-whitespace text after.
                    word += c.toLocaleLowerCase();
                    state = states.Word;
                }

                break;

            case states.Word:

                if( c == "." ) {

                    word = specialCaseWords( word );
                    output += word;
                    output += c;
                    word = "";
                    state = states.EndOfSentence;

                } else if( !( /\s/.test( c ) ) ) { // if char is NOT whitespace

                    // TODO: See if `c` is punctuation, and if so, call specialCaseWords(word) and then add the puncutation

                    word += c.toLocaleLowerCase();
                }
                else {
                    // char IS whitespace (e.g. at-end-of-word):

                    // look at the word we just reconstituted and see if it needs any special rules
                    word = specialCaseWords( word );
                    output += word;
                    word = "";

                    state = states.Whitespace;
                }

                break;
        }//switch
    }//for

    output += word;

    return output;
}

score 0 · Answer 10 · edited May 07 '18 at 00:37

0

On each line this script will print ..... Sunday Monday Tuesday Wednesday Thursday Friday Saturday.

let rg = /(^\w{1}|\.\s*\w{1})/gi;

const days = ['sunday', 'monday', 'tuesday', 'wednesday', 'thursday', 'friday', 'saturday'];

for(let day of days) {
    console.log(day.replace(rg, function(toReplace) {
    return toReplace.toUpperCase();
}))

edited May 07 '18 at 00:37

answered May 06 '18 at 20:05

Tanuj

1

On each line It will print ..... Sunday Monday Tuesday Wednesday Thursday Friday Saturday – Tanuj May 06 '18 at 20:06
Why don't you add the clarification for your answer in the answer itself instead of as a comment? – FrankS101 May 06 '18 at 20:30

score 0 · Answer 11 · answered Aug 10 '22 at 15:10

0

function toTitleCase(str) {
  if (!str) return "";
  return str
    .replace(/(?:^\w|[A-Z]|\b\w)/g, function (word, index) {
      return index === 0 ? word.toUpperCase() : word.toLowerCase();
    })
    .replace(/\s+/g, "");
}

answered Aug 10 '22 at 15:10

Oumerzoug Haitham

27
2

Can you please add some context and explanation to this answer thanks. – Nathaniel Flick Aug 11 '22 at 22:29

Convert string to sentence case in javascript

11 Answers11

Here's my modification of this post which was for changing to Title Case.

Linked

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