count occurrence of a character in a string

surya · #1 (**permalink**) September 11th, 2008, 02:25 AM

How to count the occurrence of character in a string in javascript?

thanx in advance

Old Pedant · #2 (**permalink**) September 11th, 2008, 02:07 PM

Trivial:

var theString = "Now is the time for all good men to come to!";

alert("There are " + (theString.split(/o/g).length - 1) + "letter o's in the string");

Split the string on the chosen letter and then the length of the resulting array is obviously one more than the number of occurrences of the letter.

ectar · #3 (**permalink**) November 20th, 2008, 09:31 PM

Quote:

quote:Originally posted by Old Pedant
Trivial:

var theString = "Now is the time for all good men to come to!";

alert("There are " + (theString.split(/o/g).length - 1) + "letter o's in the string");

Split the string on the chosen letter and then the length of the resulting array is obviously one more than the number of occurrences of the letter.

I had the same problem and have searched and found a lot of solution, but yours is, by far, most simple.
Thank you! (registered just to say this :) )

Old Pedant · #4 (**permalink**) November 20th, 2008, 09:45 PM

LOL! You are more than welcome!

My aim is to try to write SIMPLE code.

Jonathan Aquino · #5 (**permalink**) September 22nd, 2010, 06:04 PM

This technique does not always work. For example, in IE7,

Code:

'ooo'.split(/o/g).length-1

returns -1, not 3.

On the other hand, the following will work:

Code:

'ooo'.replace(/[^o]/g, '').length

Old Pedant · #6 (**permalink**) September 22nd, 2010, 06:24 PM

Fascinating! How right you are. JS split does not work the same as Java split.

It's truly ugly.

Try doing:

Code:

alert( "ooo".split(/o/g) );

And you get a blank string.

APPARENTLY, the split *does* work, but then JS decides that any null elements in the resultant array aren't really there and consolidates them out of existence.

I have *NEVER* seen this documented anywhere!!

Okay, it's not quite as compact, but it's still pretty simple:

Code:

<script>
var s = "oooooo";
var re = /o/g;
for( var c = 0; re.exec(s); ++c );
alert(c);
</script>

brook.monroe · #7 (**permalink**) May 7th, 2012, 04:23 PM

There's no requirement that split() take a regular expression.

"ooo".split("o")-1

works just fine to get the letter count. That leads me to

String.prototype.count = function (srch)
{
return this.split(srch).length - 1;
};

I haven't done an exhaustive suite of tests, but I think it will work.

Need to download code?

Navigation