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 qu

Answer 1

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();
});

Answer 2

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>

Answer 3

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"))

Answer 4

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;
}

Answer 5

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();
}))

Answer 6

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.