Make a character capitalize within a strin in javascript not working

Question

I am trying to capitalize a character within a string in javascript, my codes are :

<button onclick="myFunction()">Try it</button> <script> function myFunction() { var str = "string"; for(m = 0; m < str.length; m++){ if(str[m] == "r"){ str[m+1] = str[m+1].toUpperCase(); } } alert(str); } </script>

So what I am trying to do is, if the character is r,capitalize the next character. But is not woking means its the same string alerting.

AFAIR, I don't think you can modify it using str[x]=.... Use str.substring along with toUpperCase — anishsane
– anishsane, Commented May 19, 2014 at 6:16
There is a SO that seems to be the same question Here but I like @elclanrs' answer better... — Ballbin
– Ballbin, Commented May 19, 2014 at 6:20

anishsane · Accepted Answer · 2014-05-19 06:21:44Z

6

Strings in JavaScript are immutable, you need to create a new string and concatenate:

function myFunction() { var str = "string"; var res = str[0]; for(var m = 1; m < str.length; m++){ if(str[m-1] == "r"){ res += str[m].toUpperCase(); } else { res += str[m]; } } }

But you could simply use regex:

'string'.replace(/r(.)/g, function(x,y){return "r"+y.toUpperCase()});

edited May 19, 2014 at 6:21

anishsane

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answered May 19, 2014 at 6:16

elclanrs

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4 Comments

dmullings Over a year ago

he wants the character after the r to be upper case, not the r

elclanrs Over a year ago

Oh I think I misunderstood the question a bit, thx @anishsane

V.J. Over a year ago

@eclanrs He want to Capitalize the next character. Not "r"

elclanrs Over a year ago

@anishsane, yeah, but I wanted to demonstrate the callback, because the regex could be dynamic.

Fizer Khan · Accepted Answer · 2014-05-19 07:02:55Z

String are immutable. So You can convert string to array and do the replacements and then convert array to string. Array are mutable in Javascript.

var str = "string".split(''); for(m = 0; m < str.length - 1; m++){ if(str[m] == "r"){ str[m+1] = str[m+1].toUpperCase(); } } alert(str.join(''));

Najib · Accepted Answer · 2014-05-19 06:48:25Z

0

Try this

<script> function myFunction() { var p=''; var old="r"; var newstr =old.toUpperCase(); var str="string"; while( str.indexOf(old) > -1) { str = str.replace(old, newstr); } alert(str); } </script>

But you it will not work in alart. Hope it helps

edited May 19, 2014 at 6:48

answered May 19, 2014 at 6:18

Najib

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2 Comments

anishsane Over a year ago

Not "entire string".toUpperCase()... He wants a specific character to be upper cased.

Najib Over a year ago

sorry i edited the answer it will work now and @V.J alert can also show the uppercase string was my fault. please apologize my mistake.

Shakeel · Accepted Answer · 2014-05-19 06:56:41Z

var str = "string"; for(m = 0; m < str.length; m++){ // loop through all the character store in varable str. if(str[m] == "r") // check if the loop reaches the character r. { alert(str[m+1].toUpperCase()); // take the next character after r make it uppercase. } }

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